renamed SkSL texture() and process() to sample()

Bug: skia:
Change-Id: I2ae0caf08f8434302cae8151ae1ea0fda8d56928
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/230397
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
43 files changed