all: move standalone libraries to libs/ subdirectory

The root dir of our repository has grown quite a lot the past few months.

I'd like to make it more clear where the bulk of the engine lives (`src/`) and
also make it more clear which Mach libraries are consumable as standalone projects.

As for the name of this directory, `libs` was my first choice but there's a bit of
a convention of that being external libraries in Zig projects _today_, while these
are libraries maintained as part of Mach in this repository - not external ones.

We will name this directory `libs`, and if we have a need for external libraries
we will use `external` or `deps` for that directory name. I considered other names
such as `components`, `systems`, `modules` (which are bad as they overlap with
major ECS / engine concepts), and it seems likely the official Zig package manager
will break the convention of using a `libs` dir anyway.

Performed via:

```sh
mkdir libs/
git mv freetype libs/
git mv basisu libs/
git mv gamemode libs/
git mv glfw libs/
git mv gpu libs/
git mv gpu-dawn libs/
git mv sysaudio libs/
git mv sysjs libs/
git mv ecs libs/
```

git-subtree-dir: glfw
git-subtree-mainline: 0d5b853443
git-subtree-split: 572d1144f11b353abdb64fff828b25a4f0fbb7ca

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

git mv ecs libs/

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

libs/sysaudio/soundio/enums.zig

@@ -0,0 +1,149 @@
+const c = @import("c.zig");
+
+pub const ChannelId = enum(u7) {
+    invalid = c.SoundIoChannelIdInvalid,
+
+    front_left = c.SoundIoChannelIdFrontLeft,
+    front_right = c.SoundIoChannelIdFrontRight,
+    front_center = c.SoundIoChannelIdFrontCenter,
+    lfe = c.SoundIoChannelIdLfe,
+    back_left = c.SoundIoChannelIdBackLeft,
+    back_right = c.SoundIoChannelIdBackRight,
+    front_left_center = c.SoundIoChannelIdFrontLeftCenter,
+    front_right_center = c.SoundIoChannelIdFrontRightCenter,
+    back_center = c.SoundIoChannelIdBackCenter,
+    side_left = c.SoundIoChannelIdSideLeft,
+    side_right = c.SoundIoChannelIdSideRight,
+    top_center = c.SoundIoChannelIdTopCenter,
+    top_front_left = c.SoundIoChannelIdTopFrontLeft,
+    top_front_center = c.SoundIoChannelIdTopFrontCenter,
+    top_front_right = c.SoundIoChannelIdTopFrontRight,
+    top_back_left = c.SoundIoChannelIdTopBackLeft,
+    top_back_center = c.SoundIoChannelIdTopBackCenter,
+    top_back_right = c.SoundIoChannelIdTopBackRight,
+
+    back_left_center = c.SoundIoChannelIdBackLeftCenter,
+    back_right_center = c.SoundIoChannelIdBackRightCenter,
+    front_left_wide = c.SoundIoChannelIdFrontLeftWide,
+    front_right_wide = c.SoundIoChannelIdFrontRightWide,
+    front_left_high = c.SoundIoChannelIdFrontLeftHigh,
+    front_center_high = c.SoundIoChannelIdFrontCenterHigh,
+    front_right_high = c.SoundIoChannelIdFrontRightHigh,
+    top_front_left_center = c.SoundIoChannelIdTopFrontLeftCenter,
+    top_front_right_center = c.SoundIoChannelIdTopFrontRightCenter,
+    top_side_left = c.SoundIoChannelIdTopSideLeft,
+    top_side_right = c.SoundIoChannelIdTopSideRight,
+    left_lfe = c.SoundIoChannelIdLeftLfe,
+    right_lfe = c.SoundIoChannelIdRightLfe,
+    lfe2 = c.SoundIoChannelIdLfe2,
+    bottom_center = c.SoundIoChannelIdBottomCenter,
+    bottom_left_center = c.SoundIoChannelIdBottomLeftCenter,
+    bottom_right_center = c.SoundIoChannelIdBottomRightCenter,
+
+    // Mid/side recording
+    ms_mid = c.SoundIoChannelIdMsMid,
+    ms_side = c.SoundIoChannelIdMsSide,
+
+    // first order ambisonic channels
+    ambisonic_w = c.SoundIoChannelIdAmbisonicW,
+    ambisonic_x = c.SoundIoChannelIdAmbisonicX,
+    ambisonic_y = c.SoundIoChannelIdAmbisonicY,
+    ambisonic_z = c.SoundIoChannelIdAmbisonicZ,
+
+    // X-Y Recording
+    x_y_x = c.SoundIoChannelIdXyX,
+    x_y_y = c.SoundIoChannelIdXyY,
+
+    headphones_left = c.SoundIoChannelIdHeadphonesLeft,
+    headphones_right = c.SoundIoChannelIdHeadphonesRight,
+    click_track = c.SoundIoChannelIdClickTrack,
+    foreign_language = c.SoundIoChannelIdForeignLanguage,
+    hearing_impaired = c.SoundIoChannelIdHearingImpaired,
+    narration = c.SoundIoChannelIdNarration,
+    haptic = c.SoundIoChannelIdHaptic,
+    dialog_centric_mix = c.SoundIoChannelIdDialogCentricMix,
+
+    aux = c.SoundIoChannelIdAux,
+    aux0 = c.SoundIoChannelIdAux0,
+    aux1 = c.SoundIoChannelIdAux1,
+    aux2 = c.SoundIoChannelIdAux2,
+    aux3 = c.SoundIoChannelIdAux3,
+    aux4 = c.SoundIoChannelIdAux4,
+    aux5 = c.SoundIoChannelIdAux5,
+    aux6 = c.SoundIoChannelIdAux6,
+    aux7 = c.SoundIoChannelIdAux7,
+    aux8 = c.SoundIoChannelIdAux8,
+    aux9 = c.SoundIoChannelIdAux9,
+    aux10 = c.SoundIoChannelIdAux10,
+    aux11 = c.SoundIoChannelIdAux11,
+    aux12 = c.SoundIoChannelIdAux12,
+    aux13 = c.SoundIoChannelIdAux13,
+    aux14 = c.SoundIoChannelIdAux14,
+    aux15 = c.SoundIoChannelIdAux15,
+};
+
+pub const ChannelLayoutId = enum(u5) {
+    mono = c.SoundIoChannelLayoutIdMono,
+    stereo = c.SoundIoChannelLayoutIdStereo,
+    _2point1 = c.SoundIoChannelLayoutId2Point1,
+    _3point0 = c.SoundIoChannelLayoutId3Point0,
+    _3point0_back = c.SoundIoChannelLayoutId3Point0Back,
+    _3point1 = c.SoundIoChannelLayoutId3Point1,
+    _4point0 = c.SoundIoChannelLayoutId4Point0,
+    quad = c.SoundIoChannelLayoutIdQuad,
+    quadSide = c.SoundIoChannelLayoutIdQuadSide,
+    _4point1 = c.SoundIoChannelLayoutId4Point1,
+    _5point0_back = c.SoundIoChannelLayoutId5Point0Back,
+    _5point0_side = c.SoundIoChannelLayoutId5Point0Side,
+    _5point1 = c.SoundIoChannelLayoutId5Point1,
+    _5point1_back = c.SoundIoChannelLayoutId5Point1Back,
+    _6point0_side = c.SoundIoChannelLayoutId6Point0Side,
+    _6point0_front = c.SoundIoChannelLayoutId6Point0Front,
+    hexagonal = c.SoundIoChannelLayoutIdHexagonal,
+    _6point1 = c.SoundIoChannelLayoutId6Point1,
+    _6point1_back = c.SoundIoChannelLayoutId6Point1Back,
+    _6point1_front = c.SoundIoChannelLayoutId6Point1Front,
+    _7point0 = c.SoundIoChannelLayoutId7Point0,
+    _7point0_front = c.SoundIoChannelLayoutId7Point0Front,
+    _7point1 = c.SoundIoChannelLayoutId7Point1,
+    _7point1_wide = c.SoundIoChannelLayoutId7Point1Wide,
+    _7point1_wide_back = c.SoundIoChannelLayoutId7Point1WideBack,
+    octagonal = c.SoundIoChannelLayoutIdOctagonal,
+};
+
+pub const Backend = enum(u3) {
+    none = c.SoundIoBackendNone,
+    jack = c.SoundIoBackendJack,
+    pulseaudio = c.SoundIoBackendPulseAudio,
+    alsa = c.SoundIoBackendAlsa,
+    coreaudio = c.SoundIoBackendCoreAudio,
+    wasapi = c.SoundIoBackendWasapi,
+    dummy = c.SoundIoBackendDummy,
+};
+
+pub const Aim = enum(u1) {
+    input = c.SoundIoDeviceAimInput,
+    output = c.SoundIoDeviceAimOutput,
+};
+
+pub const Format = enum(u5) {
+    invalid = c.SoundIoFormatInvalid,
+    S8 = c.SoundIoFormatS8,
+    U8 = c.SoundIoFormatU8,
+    S16LE = c.SoundIoFormatS16LE,
+    S16BE = c.SoundIoFormatS16BE,
+    U16LE = c.SoundIoFormatU16LE,
+    U16BE = c.SoundIoFormatU16BE,
+    S24LE = c.SoundIoFormatS24LE,
+    S24BE = c.SoundIoFormatS24BE,
+    U24LE = c.SoundIoFormatU24LE,
+    U24BE = c.SoundIoFormatU24BE,
+    S32LE = c.SoundIoFormatS32LE,
+    S32BE = c.SoundIoFormatS32BE,
+    U32LE = c.SoundIoFormatU32LE,
+    U32BE = c.SoundIoFormatU32BE,
+    float32LE = c.SoundIoFormatFloat32LE,
+    float32BE = c.SoundIoFormatFloat32BE,
+    float64LE = c.SoundIoFormatFloat64LE,
+    float64BE = c.SoundIoFormatFloat64BE,
+};