[Ravenwood] Merge "ravenwood-helper-runtime" into "ravenwood-junit-impl"

Also make sure all Ravenwood java code is either built with
`sdk_version: "core_current"` or java_library_host.

Bug: 292141694
Flag: EXEMPT host side change only
Test: f/b/r/scripts/run-ravenwood-tests.sh
Change-Id: Ifb090a4f11735c80fc980944a20729861369d054