insights: behaviour for search queries with multiple capturing groups

Created by: leonore

from https://github.com/sourcegraph/sourcegraph/pull/40714#discussion_r954887008

we need to confirm

• how an aggregation over multiple capture groups will behave (expected behaviour is it will behave like capture group insights and just append the values to the result)
• and whether this is a change worth making for the scope

/cc @joelkw @felixfbecker @vovakulikov @unclejustin