Explicitly detect static recursion in SkSL

This relaxes our rules to allow calls to declared (but not yet defined)
functions. With that rule change, we have to specifically detect static
recursion and produce an error.

Bug: skia:12137
Change-Id: I39cc281fcd73fb30014bc7b43043552623727e03
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/431537
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
16 files changed