On the MR list page, we like to display how many issues were found from
the filtered search query *in total*. However, especially when the
filter includes conditions on the MR title or description, this can be
very expensive to calculate, and involve reading gigabytes of text data
from the database.

As long as the data is already in the page cache, this usually finishes
within the 15-second timeout on GitLab.com, but if the database cache
is cold, a statement timeout is the usual occurrence.

More generally, it's not very clever to spend so much time calculating
a piece of information with marginal value.

This MR applies a shorter limit to the counting statements and provides
for graceful fallback to a '?' value, with a nice tooltip, if the query
times out. This means we're able to view the results in a reasonable
time, rather than the page taking a long time to load, or not loading
at all.