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/gamemode/gamemode.zig

@@ -0,0 +1,76 @@
+//! Note: All the above requests can be blocking - dbus requests can and will block while the daemon
+//! handles the request. It is not recommended to make these calls in performance critical code
+
+pub const c = @import("gamemode_client.zig");
+
+pub const GamemodeError = error{
+    RequestFailed,
+    RequestRejected,
+    QueryFailed,
+};
+
+pub const GamemodeStatus = enum(c_int) {
+    Inactive = 0,
+    Active = 1,
+    /// Gamemode is active and the client is registered
+    ActiveAndRegistered = 2,
+};
+
+/// Request gamemode starts
+pub fn requestStart() GamemodeError!void {
+    if (c.gamemode_request_start() == -1)
+        return GamemodeError.RequestFailed;
+}
+
+/// Request gamemode ends
+pub fn requestEnd() GamemodeError!void {
+    if (c.gamemode_request_end() == -1)
+        return GamemodeError.RequestFailed;
+}
+
+/// Query the current status of gamemode
+pub fn queryStatus() GamemodeError!GamemodeStatus {
+    const status = c.gamemode_query_status();
+    if (status == -1)
+        return GamemodeError.QueryFailed;
+
+    return @intToEnum(GamemodeStatus, status);
+}
+
+/// Request gamemode starts for another process
+pub fn requestStartFor(pid: c.pid_t) GamemodeError!void {
+    const res = c.gamemode_request_start_for(pid);
+    if (res == 0) {
+        return;
+    } else if (res == -1) {
+        return GamemodeError.RequestFailed;
+    } else if (res == -2) {
+        return GamemodeError.RequestRejected;
+    }
+}
+
+/// Request gamemode ends for another process
+pub fn requestEndFor(pid: c.pid_t) GamemodeError!void {
+    const res = c.gamemode_request_end_for(pid);
+    if (res == 0) {
+        return;
+    } else if (res == -1) {
+        return GamemodeError.RequestFailed;
+    } else if (res == -2) {
+        return GamemodeError.RequestRejected;
+    }
+}
+
+/// Query the current status of gamemode for another process
+pub fn queryStatusFor(pid: c.pid_t) GamemodeError!GamemodeStatus {
+    const status = c.gamemode_query_status_for(pid);
+    if (status == -1)
+        return GamemodeError.QueryFailed;
+
+    return @intToEnum(GamemodeStatus, status);
+}
+
+/// Get an error string
+pub fn errorString() []const u8 {
+    return @import("std").mem.sliceTo(c.gamemode_error_string(), 0);
+}