Remove SkSL portions of SkCapabilities when SkSL is not enabled

Also fix various compile issues if you try to compile w/o SkSL.

Change-Id: I9a5a176254184a04f4c8af93a8dca958c8c69fee
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/542142
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
5 files changed