When query panels overheat, degrade them and show a warning

Summary:
Depends on D20334. Ref T13272. After recent changes to make overheating queries throw by default, dashboard panels now fail into an error state when they overheat.

This is a big step up from the hard-coded homepage panels removed by D20333, but can be improved. Let these panels render partial results when they overheat and show a human-readable warning.

Test Plan:

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13272

Differential Revision: https://secure.phabricator.com/D20335