WASAPI multi-channel microphone input

[SleeeepyZhou]

Support multi-channel microphone input by downmixing to stereo

• Enhanced the WASAPI audio driver to support microphones with any number of channels.
• This modification ensures compatibility with a broader range of multi-channel microphones, allowing for more versatile input handling in engine.
• Regarding “WASAPI: unsupported channel count in microphone!” error.

Related issues
This is a pull that I created in the Godot.

I tried compiling and testing the four channel microphone on my laptop, and it turned out to be error free. This enables the successful use of multi-channel microphones in Godot.

I made the assumption that the microphone might have a potential configuration with odd channels (e.g., Left, Right, Center), although such configurations are uncommon (in some professional audio equipment). The goal was to ensure that the microphone is at least usable within Godot, regardless of the channel count. The WASAPI documentation itself doesn't explicitly specify how multi-channel microphones should be handled, so I aimed for a more general solution to accommodate various configurations.

Thank you for reviewing !

[Spartan322]

This needs to be squashed, aside from that, do you have people who we can speak to who can test the robustness of this? The more people we have to test, especially in some of the odd configurations, the better.

[SleeeepyZhou]

This needs to be squash, aside from that, do you have people who we can speak to who can test the robustness of this? The more people we have to test, especially in some of the odd configurations, the better.

Oh yes, it seems to require three approvals to merge. In addition, this fix is for microphones with more than two channels (such as my laptop which has five channels). I allocated the extra channels, and if there is one left, I evenly distributed them. This fix runs well on my laptop.
You can view the pulls I previously initiated in the Godot repository.

[Spartan322]

Yeah I just wanted to get as many testers I can speak on this as possible, other than that it just needs to be squashed down to one PR and I don't see a reason it wouldn't be merged quick.