ref(grouping): Simplify parameterizer code

[lobsterkatie]

This is handful of refactors to the parameterization code, to make it a bit simpler and more testable.

• Allow ParameterizationRegex objects to be passed directly to parameterizer during initialization rather than always using the default set. (This should make it easier to test, so we don't have to do a bunch of mocking.) If none are passed, the default set will still be used.

• Create the final regex directly in __init__ rather than in a separate method.

• When deciding if the experimental parameterizer is actually experimental, look at the regexes themselves rather than at the regex maps.

• When deciding whether to skip testing the experimental parameterizer, look directly at it rather than comparing the regex maps.

• Remove the now-unused regex maps.

• Rename a number of things.