SkSL function inlining

This first pass adds "one size fits all" function inlining, without any
allowances for simple functions that don't need all of this machinery
in place. Followup CLs will simplify common cases by e.g. not storing
arguments in variables if they're already variables and not wrapping
the function body in a loop when it isn't necessary.

Change-Id: I4fd8c1655ff48b9e4708bcca03a506df34ceadd9
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/290127
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
53 files changed