insights: surface timeout limit hit to end users in the UI

Created by: Joelkw

It's possible to hit a timeout but not see that in the UI for insights and mistakenly assume your insight is correct.

This issue is limited on large results sets/searches that timeout.

We should surface this in the UI if a snapshot or insight has hit this limit. Ideally we can do per-point but otherwise per-insight is fine.

cc @AlicjaSuska we mostly need a design for this; I believe we track this in dirtyqueries in the db somehow already. (if this is small, we will prioritize this for sometime in later Q3).

/cc @joelkw @felixfbecker @vovakulikov @unclejustin