R1:9d1af762d518

In summary interfaces, don't render very large inline remarkup details for unit test messages

Summary: Ref T10635. An install with large blocks of remarkup (4MB) in test details is reporting slow page rendering. This is expected, but I've mostly given up on fighting this unless I absolutely have to. Degrade the interface more aggressively.

Test Plan:
- Submitted a large block of test details in remarkup format.
- Before patch: they rendered inline.
- After patch: degraded display.
- Verified…