Added cachingParser back to *all* the parser tests, fixed a couple of
differences with the normal parser, and added a couple of tests so that
any cachingParser-related file has 100% coverage. Also move the remaining
get_matches tests inside parserTests, and specify the parser used in case of failure.
This also adds a new base class for parser-related tests with a couple
of util methods.
Bug: T201193
Change-Id: I980aec3481a52ecc35f1811a366014a5581a7cdb
