Add mixer.get_driver

[ankith26]

While working on #2733 I realised that we don't actually have the mixer analogue to display.get_driver(). This PR adds mixer.get_driver to find out the current audio driver being used.

[Starbuck5]

Seems legit, looks good

• API isn't changing in SDL3 ✔️ (well, the SDL_AUDIODRIVER env is moving to SDL_AUDIO_DRIVER, but we can put in a note for that)
• API doesn't already exist in _sdl2.audio ✔️
• Test passes locally ✔️
• Exhaustive list of drivers checks out against a skim of source code ✔️

Should get SDL_GetAudioDriver and SDL_GetNumAudioDrivers be ported too, into a method to get a list of available drivers? That way a user setting SDL_AUDIODRIVER could see what the options are.

[Starbuck5]

Should get SDL_GetAudioDriver and SDL_GetNumAudioDrivers be ported too, into a method to get a list of available drivers? That way a user setting SDL_AUDIODRIVER could see what the options are.

It seems like this would help test #2733

[MyreMylar]

LGTM 👍

Tested with:

import pygame

pygame.init()
print(pygame.mixer.get_driver())

>> wasapi

[ankith26]

Should get SDL_GetAudioDriver and SDL_GetNumAudioDrivers be ported too, into a method to get a list of available drivers? That way a user setting SDL_AUDIODRIVER could see what the options are.

Sounds like a good idea. We could also give display the same treatment. Maybe we could export this as a list, instead of having to export two separate functions.

[Starbuck5]

That's what I had in mind.