bazel: Refactor SkPicture files into own filegroups.

The existing *.gni files have all SkPicture files in a separate
file list in //gn/core.gni. Split out SkPicture files into own
Bazel filegroups so that they can be mapped to legacy GNI
variables.

Bug: skia:13485
Change-Id: Ic2bac79ca3046d9f3a81bea35f4bb5fdaa31ae88
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/567298
Reviewed-by: Kevin Lubick <kjlubick@google.com>
3 files changed