Add initial support for WebGL compressed textures
This patch is an initial implementation of WebGL compressed texture support, it contains
- functions for registering and querying compressed texture extensions
- initial implementation of `CompressedTexImage2D` and `CompressedTexSubImage2D` and their parameter validation
- implementation of S3TC (DXT1, DXT3, DXT5) and ETC1 extensions as examples
What's still missing:
- some of the parameter validation steps are missing
- the pixel comparison tests fail for more complex cases (I'm probably missing something trivial at the GL calls)
Related: #10209 and #20594
cc @jdm @zakorgy
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] Related issues: #10209, #20594
- [x] There are tests for these changes
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Create CanvasRect for OffscreenCanvas
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Created CanvasRect fot OffscreenCanvas and Updated Testcases
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We use that to send only the pixels that will be actually drawn to the
canvas thread in CanvasRenderingContext2d::PutImageData.
We also make the canvas thread byte swap and premultiply colours in-place.
Various webgl fixes for framebuffer attachment test
These changes resolve all panics on macOS when running framebuffer-object-attachment.html in headless and headful testing.
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] There are tests for these changes OR
- [x] Fixes#13710. Fixes#20570.
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