* Split out cache plugin unit tests.
* Rename unit tests to match code under test.
* Relocate unit test code to match code under test.
* Another rename.
* Update sanity ignores.
* Move ansible.compat.tests to test/units/compat/.
* Fix unit test references to ansible.compat.tests.
* Move builtins compat to separate file.
* Fix classification of test/units/compat/ dir.
This offers an optimization that allows loading larger
inventories of various structure by improving the
scaling laws involved for adding hosts and groups.
The primary speed benefit is the elimination of duplicate
recusion from traversing converging paths.
