Move 'is builtin code' flag into the ProgramConfig.

This makes the flag accessible from anywhere with a Context. Previously,
it was known by both the DSLWriter and IRGenerator, but otherwise
inaccessible unless manually passed to each function that needed it.

Change-Id: I029715c9049cb0810cb2960864632a82064921f9
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/455656
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
7 files changed