dashboard/app: allow renaming/bucketing bugs

[dvyukov]

We need to put all non-KMSAN bugs on KMSAN syzbot instances into the same bug. It happens so that we mostly interest in KMSAN bugs on KMSAN instances. The rest tend to induced crashes, bugs that we already reported on KASAN instances but that look differently, etc.
The simplest say to do this seem to be allow config hooks in dashboard app that could look at a crash and rename it to e.g. "non-KMSAN bug". Additionally it need to force "no repro" for such crashes.

[dvyukov]

@ramosian-glider