New extra and helper methods to set screenlock to a specific complexity level

- updated complexity bucket metrics order and comments so that the
buckets metrics are sorted in ascending order of quality
- added helper method to sanitize complexity level (default to none if
invalid)
- added helper method to get min quality allowed at a complexity level
- added helper method to return the minimum metrics to fulfil minimum complexity
and dpm requirements

Bug: 111173457
Test: atest FrameworksCoreTests:PasswordMetricsTest
      manual test with TestDpc (ag/5901733)

Change-Id: Icf7c81bea0b66a47c4ee5913cfa0e713b3fa77b6