[Ravenwood] Move stats generation out of critical path

Move stats generation into its own genrule outside of the bytecode
processing pipeline to improve efficiency.

We also take the chance to clean up Framework.bp.

Bug: 292141694
Flag: EXEMPT host side change only
Test: f/b/r/scripts/run-ravenwood-tests.sh
Change-Id: Ibe09d88f3f3b5dc8f5fc29e8be2bdd3a712538f5