insights: generate drilldown queries for aggregation matches

Created by: coury-clark

Closes https://github.com/sourcegraph/sourcegraph/issues/40370

Generate drilldown queries (to get more specific) for aggregation match groups. If the drilldown query cannot be generated, fallback to the original query.

This has some rough areas (for example lots of repeated / duplicated query parsing). I have a query builder refactor I'm working on the side to clean this up and improve it. That said this functionality isn't blocked by that refactor.

Additionally, I believe the capture group aggregation isn't implemented yet, so obviously will need to wait to try out on that.

One note about author drilldown - it seems that we may need to escape for whitespace as well as regexp characters, as whitespace will cause the query to change semantics and break. For example if the match is Santa Claus and it tries to generate author:Santa Claus, actually it needs author:Santa\ Claus

Test plan

Tested manually for repo / filter / author. Will circle back to this for tests when the functionality is implemented.