case sensitive drilldowns

Created by: coury-clark

Closes #41018 (closed) Closes https://github.com/sourcegraph/sourcegraph/issues/41442

I also added some tests around building the drilldown query that were missing from a previous PR. You'll notice these don't include scenarios for regexp without capture groups, and that is because there seems to be a bug that needs to be fixed (issue tbd).

You'll also notice that when drilldown queries are placed into the search box they have an extra space now. This is because the search box pulls out the case field to toggle the case button, but leaves behind an extra whitespace. https://github.com/sourcegraph/sourcegraph/issues/41452

Test plan

insights type:commit -> type:commit author:(^Vova Kulikov$) insights Case sensitivity is turned on (but not visible in the search box)

insights type:commit -> type:commit author:^coury-clark$ insights