Add a test role to validate module functionality

Replace calls to the sdk cloud layer to use the proxy layer.

Update module parameters to use names matching the sdk. Keep aliases for
old values.

Remove _scrub_results, no longer necessary with proxy layer.

Move check mode outside of main flow to keep the module readable.

Refactor code to handle fields that should be ignored.

Simplify return value from _system_state_change_details.

Inline calls to fetch existing quotas.

Remove metaprogramming calls to cloud layer methods, as the proxy layer
doesn't have the same consistent API.

Remove handling for case where neutron throws exception when unsetting
quotas that aren't set. This is validated in the test role.

Ensure return values are dicts.

Replace exception handler with conditionals which allows us to drop the
dependency on keystoneauth1 library and is much more correct than
catching all exceptions and always printing the same error even on
unrelated exceptions.

Story: 2010099
Task: 45654

Change-Id: I5eda8e476a4e779382e6c63f5982504d5951501d