Add NV12 support (V4L2 needs work)

[Muny]

Spurred by #132

This is my first attempt at adding NV12 support.

Tested on Win11 with .NET 8.0 with an Elgato CamLink 4K.

I couldn't quite figure out the code generator for the V4L2 native methods, so that will need support. I'm willing to help test that on x86_64 Linux once that's working.

To make it easier to support new frame formats in the future, it may be wise to make some use of a library like libyuv (just a suggestion, I know you want to keep the number of dependencies low)

[kekyo]

Excellent, thanks for the improvement!

The reason why NV12 symbols are not enumerated in V4L2 is because there are no hard-coded symbols in the following code in the Generator:

FlashCap/FlashCap.V4L2Generator/Program.cs

Line 68 in 854186a

"V4L2_PIX_FMT_ABGR32",

We can update it by adding NV12 here and running the generator on each platform, but this will be painstaking as it needs to be supported on all platforms :)
Minor platforms may take some time to prepare, but I will take care of this task. It will probably take several days.

[kekyo]

@Muny I'm continuing these works, could you please rebase on current devel?

[kekyo]

@kakulukiya45t654645 We are working on this issue to update the V4L2 interoperability code, we also need to update and verify in the loongarch64 environment, but I do not have the environment. Could you please update it when we are ready?

What we need is to re-run the script dumper.sh, make the necessary adjustments to the build (perhaps a few lines need to be hacked to success compilation), and confirm that it works in a real environment (try with WinForms or Avalonia sample code).

[kekyo]

@Muny Sorry later thanks! I merged temporary and will create new branch for remaining works.