Initial land of DSLParser

The DSLParser is an alternative to the existing SkSLParser which goes
directly to IR code using the SkSL DSL. It is substantially faster and
simpler than the existing parser->IRGenerator pipeline, but not yet
feature complete nor fully tested.

Change-Id: Iee45e9b527a3b88faa2ea74fc512051c8a38c5d4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/400622
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
23 files changed