Large simplification of the CType mapper logic in SkSL

- Arrays were unused
- Each ctype was used with exactly one mapper - remove the SkSL type
  list
- After that, the mapper was just a key + value, so make it just a value
  and use a map (rather than vector)

Change-Id: Ibc150ecc9ac9724ecd1e7056614ca5836ce99d5b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/409998
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
23 files changed