moved SkSL Block's data into IRNode

Change-Id: Id1066c7c2aeffce47fcd6823cb01a58b52e450c2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/319676
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
19 files changed