insights: web app add capture group to the "Group By" options for insight create/edit

Created by: chwarwick

Search aggregations support saving a capture group aggregation as a "group by" insight. The create and edit screens for the group by insight do not currently present the user with "Capture Group" as a grouping option.

In addition to adding the Capture Group option the query criteria should match the criteria specified for the "detect and track" insight.

depends on https://github.com/sourcegraph/sourcegraph/issues/40535

/cc @joelkw @felixfbecker @vovakulikov @unclejustin