[SDL2]: Add an ability to prevent initialization of capture devices

[Wohlstand]

Hello!

On a quick hand, I made an incomplete thing that prevents to initialize any capture devices: Wohlstand@1ad2810

Primarily it's need on modern macOS to prevent it to request "permission for microphone" which is actually not needed by me at all (and I don't even use any capture devices at all). However, this seems to be a workaround rather than a true solution of "microphone permission problem".

Maybe instead, don't initialize any capture devices before the first request on macOS especially?

[icculus]

We shouldn't be accessing capture devices (beyond enumerating them), but this might be only true in SDL3, or I might be completely wrong. I'll double-check and we can decide if a hint is necessary.

[Wohlstand]

On SDL2 this is actually a problem: in my apps I don't use audio capture at all, but macOS still asks a permission for microphone.

[Wohlstand]

And also I saw a smiliar case with other apps that use SDL2, and the problem is the same.