Migrate ProgramUsage out of SkSLAnalysis.

Change-Id: I005eccfa262ed047409cce0417f50f93fb6341a3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/456641
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
3 files changed