Stop exposing Ravenwood internal implementation to public APIs

- Consolidate all Ravenwood utils into RavenwoodRule
- Move all "host-only" code into junit-impl-src or runtime-helper-src
- Remove all reference to `RavenwoodCommonUtils` in test code.

Bug: 292141694
Flag: EXEMPT host side change only
Test: f/b/r/scripts/run-ravenwood-tests.sh
Change-Id: I939d7822651fd2e503d749ed9c7dd8b29bb79928