Roll Skia from 923d83bf1875 to 6389bfaa8344 (6 revisions)

https://skia.googlesource.com/skia.git/+log/923d83bf1875..6389bfaa8344

2021-10-04 ethannicholas@google.com Removed useless modifiersWithDefaults method from DSLParser
2021-10-04 egdaniel@google.com [graphite] Add support for Mtl Stencil/Depth Textures.
2021-10-04 ethannicholas@google.com Fixed unsupported type errors in pure DSL
2021-10-04 ethannicholas@google.com Removed unused/nonexistent methods from IRGenerator
2021-10-04 jvanverth@google.com [graphite] Add CommandBuffer creation
2021-10-04 jvanverth@google.com Clean up #includes in SkCFObject.

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https://skia-autoroll.corp.goog/r/android-master-autoroll
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https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

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Bug: b/186777432
Change-Id: I35e278bd7eae33edc47ead711578140ad8e509e1