moved SkSL FunctionDeclaration data into IRNode

Change-Id: I97a59563914c4f75f8cfdc2bd5a9ae430de9bb3c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/323881
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
19 files changed