Remove SkSL sample() intrinsic for Skia object types

Bug: skia:12302
Change-Id: Ifc107ca2cf13c1daa59521b93fe4ad1d3c215258
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/447297
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
7 files changed