Summary:
This splits up the generated file checker tests into 3, uses `.arcunit`
to specify includes when they should be triggered, uses a base class for the
shared code and cleans up some of the bazel querying to figure out targets.

Test Plan:
Made changes that should trigger the unit tests. Ran `arc unit`

Before running generate scripts:
{F132932}

After running generate scripts:
{F132933}

Reviewers: michelle, zasgar

Reviewed By: michelle

Differential Revision: https://phab.corp.pixielabs.ai/D8138

GitOrigin-RevId: 96587005672e7e7aed9d8e5d7e1f3f8137fb4b55