audio_core: Preserve front channel volume after 6 to 2 downmix

Many games report 6 channel output while only providing data for 2. We only output 2-channel audio regardless, and in the downmixing, front left/right only provide 36% of their volume. This is done assuming all of the other channels also contain valid data, but in many games they don't. This PR alters the downmixing to preserve front left/right, so volume is not lost.

This improves volume in Link's Awakening, New Super Mario Bros U, Disgaea 6, Super Kirby Clash.

[audren] Report 2 channels active rather than 1

util_shaders: Fix BindImageTexture

According to
https://gitlab.freedesktop.org/mesa/mesa/-/issues/3820#note_753371 we
need to set these to true for use with 3D textures.

Fixes BOTW teleporting on RadeonSI and iris.

common: fs: More misc. changes

GPU Memory Manager - Correct handling of non continuous backing memory.

CMakeLists: Treat -Wsign-compare as an error on GCC/Clang

Treats (un)signed comparison mismatches as errors to be consistent with MSVC

There's no point in keeping the file open after the write limit is exceeded. This allows the file to be committed to the disk shortly after it is closed and avoids redundantly checking whether or not the write limit is exceeded.

It became apparent that logging can continuously spam errors that trigger file flushing.
Since committing the files to disk is an expensive operation, this causes unnecessarily high disk usage.
As such, we will revert Flush() to the previous behavior and add a Commit() member function in the event that this behavior is needed.

This ensures that GetSize always retrieves the correct file size after a write operation.

general: Enforce multiple warnings in MSVC

service: mii: Retrieve the correct default miis.

Slightly refactor NVDEC and codecs for readability and safety

input_common: Add missing modifier callback to analog from button

Replace usages of deprecated member functions in QMouseEvent and QWheelEvent

CMakeLists: Enforce C4189 on MSVC

TextureCache: Fix 1D to 2D overlapps.

We were including the first 2 default miis which are not meant to be shown in games. With this change, we properly retrieve the 6 default miis shown in games, with 3 of each gender.

This supplements C4101 by detecting initialized but unreferenced local variables

[audio_core] Decouple audio update and processing, and process at variable rate

cmake: Improve Linux dependency checking for externals

yuzu qt, core: Support LayeredFS mods from SDMC directory

main: Add GPU Vendor name to running title bar

This lets us avoid needing to wrap external headers with #pragma warning directives for warnings we treat as errors and avoids generating warnings for external code.

Thanks to MerryMage for pointing this out.