audio: Added SDL_GetAudioDeviceProperties() and a unique-id property for it.

[icculus]

• I confirm that I am the author of this code and release it to the SDL project under the zlib license. This contribution does not contain code from other sources, including code generated by a Large Language Model ("AI").

(EDIT: this was the original text, but this now offers audio device properties instead of an API for specifically this one thing.)

This allows a best-effort option to find the same specific audio device used on a previous run of a program, even in an imperfect way. Most backends don't support this, but CoreAudio on macOS and IMMDevice on Windows can.

coreaudio: Rework device enumeration queries, acquire unique_id.

• No longer keeps multiple AudioObjectPropertyAddress objects, just change the selector for each query.
• Move string retrieval off to a separate function.
• Query for unique_id.
• If a device name is blank, don't reject the device, try to come up with a name of some sort (either the unique_id or "Unnamed audio device").

windows: Add unique audio device identifiers to IMMDevice support.

This uses the new "StableId" property on Windows 11 if available, and the device id (IMMDevice::GetId()) otherwise.

Microsoft claims that GetId() remains valid between reboots and even disconnecting and reconnecting the audio device (although I am dubious that is universally true when plugging into a different USB port, etc), but driver and OS updates might change the identifier. StableId goes further, promising that software updates won't change it, either.

This adds support to our WASAPI and DirectSound backends, if you're on at least Windows Vista. Windows XP will not offer a unique ID for devices.

Fixes #16258.

[icculus]

Debated doing this as an optional property, but we'd still have to add an API for that, since we don't have an SDL_GetAudioDeviceProperties() function at the moment (and do logical and physical devices have separate properties? etc).

But I'm not against making that change, or even just renaming the new wordy function.

[slouken]

This does seem like a perfect opportunity for properties

[icculus]

Okay, pivoting!

The specific changes are in 881f46d, but I'm squashing this down to remove the original API now.