Add a class representing texture swizzle.

Store config swizzle GrGLCaps and shader swizzles in GrGLSLCaps.

Remove GrTextureAccess's swizzle and update users of it to swizzle in their shader code.
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Committed: https://skia.googlesource.com/skia/+/1a1efeacf7cc94a8c2977114dfe230fed3efc105

Review URL: https://codereview.chromium.org/1567733005
14 files changed