[sksl][compute][spirv] Support barrier intrinsics

Implement SPIR-V codegen for workgroupBarrier and storageBarrier
intrinsics.

Bug: b/262428625
Change-Id: Ic7ea45a2108258c63d2cd0396f058efaf10ff4af
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/729099
Reviewed-by: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Arman Uguray <armansito@google.com>
6 files changed