moved SkSL If data into IRNode

Change-Id: Icccc14019ae5c87a09c8439fa1b1ae324b8e32bf
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/323777
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
17 files changed