dev/core#1374 Fix search formValue handling on contribution search

dev/core#1374 Fix search formValue handling on contribution search

This fixes 2 issues
1) Search params being lost when editing a related entity per
https://lab.civicrm.org/dev/core/issues/1374
2) force=1&sort_name=p not working in contribution search url

In digging I concluded the problem is we have 3 underlying arrays which we keep jumbling together

1) formValues - the actual submitted values, augmented by any  url passed params
2) the default values - values to load by default on the form
3) our working query params - a copy of formValues that we have prepared for the query

We need to stop mangling them. I added subtle code comments