notebooks: compute block warns on incomplete commit/diff query

Created by: rvantonder

Stacked on https://github.com/sourcegraph/sourcegraph/pull/32864

AFAIK we don't have an alert/signal for "incomplete commit/diff" results from search backend. We do have result limit hit, which is count based, but even if you go beyond the count, we will clamp to 1500 results in the search client.

Since compute uses an internal search client, and we don't have a limit hit, I'm just surfacing an alert in the compute client if we do a diff or commit search without count:all. The footgun potential of assuming complete data is greater than my concern that we'll overload the server with commit/diff searches. The searches tend to finish quickly, and I did confirm we impose the 50 repo limit on Sourcegraph.com. The search won't even execute otherwise, and that includes search that compute kicks off.

Test plan

Tested manually experimental feature