moved SkSL InterfaceBlock data into IRNode

Change-Id: If85369d978e395502b2169d605c2513a9086b57e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/326916
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
11 files changed