Move GrClipStack to skgpu::v1 namespace

Bug: skia:11837
Change-Id: I42dfaf795ec6afe9d648b0715457a3a38ef8c7a4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/439943
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
7 files changed