moved SkSL Section data into IRNode

Change-Id: I255eb58fc4e6e3b08dfd8e962ee8fe22144d4c36
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/325859
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
7 files changed