Add a way to run specific test classes/methods

You can override the above logic and run exact test classes / test
methods by setting a case-insensitive regex to
$RAVENWOOD_FORCE_FILTER_REGEX. If it's set,
only the tests that are mathing it would be executed.

For example, running with
RAVENWOOD_FORCE_FILTER_REGEX='(MyTestClass1|MyTestClass2#testFoo)'
would execute all tests in MyTestClass1, and only testFoo() in
MyTestClass2.

Bug: 292141694
Flag: TEST_ONLY
Test: $ANDROID_BUILD_TOP/frameworks/base/ravenwood/scripts/run-ravenwood-tests.sh -s
Change-Id: Ib47a751b973833824f106fa81ff94727b0c7f2d1