add: device playback information query methods

[umurgdk]

When configurations such as sample rate and number of channels are left empty there is no way to query that information back after the device is initialized with system defaults. This PR adds these methods to Device:

fn getSampleRate(device: *const Device) u32 {}
fn getPlaybackFormat(device: *const Device) Format {}
fn getPlaybackChannels(device: *const Device) u32 {}

One quick fix on memory allocation on zaudioMalloc function to manually inlining std.mem.Alignment.fromByteUnits to keep this library backward compatible with zig v0.14.0

[umurgdk]

Sorry about not checking the actual compatibility results. I've ran tests successfully on my latest fix commit on both 0.14.1 and 0.15.1