Update to new GrDirectContext::MakeMetal API

[jeremy-visionaid]

Description of Change

Update to new GrDirectContext::MakeMetal API for m124 and later.

Also, use retain for setting the pointers to prevent GrMtlBackendContext disposing the command queue.

SkiaSharp Issue

• [BUG] iOS: Crash when GC collects SKMetalView resources SkiaSharp#3178

Fixes: mono/SkiaSharp#3178

API Changes

None.

Behavioral Changes

None.

Required SkiaSharp PR

Requires mono/SkiaSharp#3258

• Test disposing GRContext does not crash for Metal backend SkiaSharp#3258

PR Checklist

• Rebased on top of skiasharp at time of PR
• Changes adhere to coding standard
• Updated documentation

[mattleibow]

Thanks for this PR.

I think it is fine to just fix the code in src/gpu/ganesh/GrDirectContext.cpp

Then we don't need to worry later.

[jeremy-visionaid]

Thanks for this PR.

I think it is fine to just fix the code in src/gpu/ganesh/GrDirectContext.cpp

Then we don't need to worry later.

Huh? But what I'm saying is that code is going to get removed upstream, then you'll get a conflict and you'll have to do this anyway...

mono/SkiaSharp#3258 (comment)