Metrics performance improvements (#10446)

* metrics-performance wip dashboard changes

* metrics-performance wip on metrics

* metrics-performance work on metrics tables

* metrics-performance wip more tables

* metrics-performance endpoints work

* metrics-performance renaming

* metrics-performance endpoints and some cleanup

* metrics-performance endpoints metrics details table populates with finding info

* metrics-performance endpoint calcs against endpoint_status instead of related finding

* metrics-performance template var fix, calculate period ranges more in line with previous offering

* metrics-perfromance refactoring

* metrics-performance remove old code, use existing helper function rather than reimplementing

* metrics-performance fix bug age determination to handle "negative" mitigation dates

* metrics-performance Updates to rename some vars, use existing functions, comments

* metrics-performance rename age entry vars to be more descriptive

* metrics-performance changes to use existing functions

* metrics-performance comments, typing, refactoring

* metrics-performance refactoring and comments

* metrics-performance type hinting, fix dashboard

* metrics-performance move metrics methods to a util module

* metrics-performance reordering imports for linter

* metrics-performance refactor

* metrics-performance remove perf class, restore some code that didn't need changing

* metrics-performance comment cleanup

* metrics-performance work on test fixes

* metrics-performance test updates

* metrics-performance test updates

* metrics-performance attempt at handing findings age determination for mysql

* metrics-performacne fix import

* metrics-performance loosen exception for finding age determination

* metrics-performance derp querysets are lazy

* metrics-performance linter fix

* metrics-performance fixes for mysql

* metrics-performance use counts for severities instead of sums to avoid null values, use correct reverse lookup on urls in accepted/closed/open tables

* metrics-performance set appropriate links on findings tables

* trigger actions

Author: dogboat