LogEntry: Make associated rev id persistent (store in logging and log_search)

LogEntry: Make associated rev id persistent (store in logging and log_search)

The implementation from 0160b410bd514681b1637ccab2b7c79158fbfb29 only
stored the associated rev id in the `recentchanges` table, which was
sufficient for its purpose of allowing patrol of these log entries and
provided some change tagging improvements, but ephemeral.

Now we also store it in `logging` and `log_search` tables, which makes
it possible to find a revision for the log entry and vice versa.

* For `log_search` we just add a row with 'associated_rev_id' as key,
  it was designed for exactly this purpose.
* For `logging` we store it in log_params field in ManualLogEntry, and
  transparently remove it from there when building a DatabaseLogEntry.

Bug: T122089
Change-Id: I559587ff77b3c94b31a6c5951287b6f9c1e167ce