R1:cd3a3bf759b1

Make Herald Rules sticky in X-Herald-Rules

Summary:
See T354. List every rule which has ever been applied in X-Herald-Rules, not
just the ones which most recently triggered.

Also some random fixes while I was debugging this:

- When conduit methods throw non-conduit exceptions, make sure they get
logged.
- Trigger the Facebook "tasks" backcompat block only if we were going to fail
(this should reduce the shakniess of the transition).
- Fix some log spew from the new field stuff.

Test Plan…