Move more GPU text classes to sktext::gpu namespace.

Moves GlyphVector, TextStrike, StrikeCache, and SubRunAllocator.

Bug: skia:13118
Change-Id: Ifa4957b5cff280f44606dc62bfd30f6a03063c07
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/536102
Reviewed-by: Greg Daniel <egdaniel@google.com>
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
44 files changed