Migrate slot/function info structs out of SkVM-specific header.

These structs would be equally useful for the SkRasterPipeline
code generator.

Change-Id: I20d19d74ae08c1730a8268170e348f6301e5e7ba
Bug: skia:13676
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/613077
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
12 files changed