Remove 565 mask data from GrStrikeCache to constexpr varialbe

Move the 565 from the GrStrikeCache to the routine that uses it.
Remove all the plumbing needed to get it there.
Remove unused variable from GrStrikeCache's ctor.

Change-Id: I6d6630ace0e22ec9c4f68e4c359beda6354c323f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/268168
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Herb Derby <herb@google.com>
11 files changed