Audio: always target 48000hz f32 audio

Resampling, which requires fairly involved (and certainly not free) filters,
is needed if the audio we are mixing does not match the sample rate of the
output device. Most OS audio APIs support resampling on their own, but have
preferred hardware formats. Most console hardware since Xbox/PS2/GC supposedly
prefers 48khz natively, but otherwise there seems to be no big preference
between 48khz or 44.1khz.

The important aspect is that we pick one, and encourage people to keep their
audio in one, so that runtime resampling is not required (both in mach itself,
and potentially without-our-knowledge in the OS audio system if we chose a
sample rate which the native hardware does not prefer.)

General guidance will be:

* `mach.Audio` module will always aim to select 48khz, f32 audio output from the
  OS APIs. Let the OS APIs do resampling, or if they do not then we can do so.
* We will prefer 48khz, f32 audio samples everywhere internally in our basic audio
  mixing etc. APIs.
* Tooling will aim to convert audio to Opus (or flac for lossless) format, with 48khz
  and number of channels depending on audio type (e.g. 1ch for most sfx, any number of
  channels for bgm, and maybe some exception for multi-channel sfx in the future.)

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

src/Audio.zig

@@ -50,7 +50,8 @@ fn init(audio: *Mod, on_state_change: mach.AnyEvent) !void {
     // TODO(audio): let people handle these errors
     // TODO(audio): enable selecting non-default devices
     const device = ctx.defaultDevice(.playback) orelse return error.NoDeviceFound;
-    var player = try ctx.createPlayer(device, writeFn, .{ .user_data = audio });
+    var player = try ctx.createPlayer(device, writeFn, .{ .user_data = audio, .sample_rate = 48000 });
+    log.info("opened audio device: channels={} sample_rate={} format={s}", .{ player.channels().len, player.sampleRate(), @tagName(player.format()) });
 
     const debug_str = std.process.getEnvVarOwned(
         allocator,