Port used limits to core API

Extension 'used limits' was extending core 'limits' API with used
resources information. So, provide such information in core API and
remove extension completely.
It does not require neither update of API router nor bump of
microversion.

Partially implements bp ext-to-core

Change-Id: I0ff71fbd0281eb2e34a9acbfc72ff8c14390e8d9
1 file changed
tree: 1ad7a6c41c7361d333aa71d14966c26b5fbe848d
  1. manila_tempest_tests/