Update "stats" generation

- Stop hardcoding test directory path in ravenwood-stats-collector.sh
- Don't count native methods kept by KeepNativeFilter as "supported"
- Hide some of the "obvious" classes and methods
  (annotations classes, Object methods, etc etc)

Flag: EXEMPT host test change only
Bug: 402797626
Test: $ANDROID_BUILD_TOP/frameworks/base/ravenwood/scripts/run-ravenwood-tests.sh -s
Change-Id: I0a12ec51cc6cc852bc2d1bde68021c34c2c8bb59