Convert and delete some old API tests

Remove the following modules:

1. `test_computeresource`
2. `test_configtemplate`
3. `test_domain`
4. `test_environments`

The first three contained no working tests and no interesting test stubs. The
existing test stubs were for goals such as creating or deleting an entity. Given
that all four relevant entities are already tested in module
`test_multiple_paths`, there is no value to the stubs.

The fourth module contains tests for creating environments with valid and
invalid names. Port these tests to module `test_environment_v2`.

Remove outdated module references from the API documentation.
I'm still not sure what the desired behaviour is. Pending some sort of response from upstream, I've just dropped in a comment explaining why the test is structured as it is.