[Ravenwood] Update system property handling

- Split out "core" system properties (the default properties we set
  during the global initialization) and "test" system properties (the
  properties defined and set through RavenwoodRule)
- Reset only the "test" system properties before each test execution
- Update the implementation to support nested RavenwoodRule in the
  future

Flag: EXEMPT host test change only
Bug: 377765941
Test: $ANDROID_BUILD_TOP/frameworks/base/ravenwood/scripts/run-ravenwood-tests.sh
Change-Id: Ia9a2ee217aa89e0f2565d14fb26e3842947e9dc7