recovery: make it transactional

Recovery used to be performed row by row. It was fine because
anyway all the persisted rows are supposed to be committed, and
should not meet any problems during recovery so a transaction
could be applied partially.

But it became not true after the synchronous replication
introduction. Synchronous transactions might be in the log, but
can be followed by a ROLLBACK record which is supposed to delete
them.

During row-by-row recovery, firstly, the synchro rows each turned
into a sync transaction. Which is probably fine. But the rows on
non-sync spaces which were a part of a sync transaction, could be
applied right away bypassing the limbo leading to all kind of the
sweet errors like duplicate keys, or inconsistency of a partially
applied transaction.

The patch makes the recovery transactional. Either an entire
transaction is recovered, or it is rolled back which normally
happens only for synchro transactions followed by ROLLBACK.

In force recovery of a broken log the consistency is not
guaranteed though.

Closes #5874