Reject shaders which mark textures/samplers as 'uniform.'

This implements a suggestion from
go/samplers-and-storage-textures-in-sksl.

Bug: b/295169976
Change-Id: Ie38ea222e509ed949cfc8f8bb9202ccb18786e76
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/746039
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Arman Uguray <armansito@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
8 files changed