If the server is upgraded from a database that was created
before MDEV-12288, and if the undo logs in the database contain
an incomplete transaction that performed an INSERT operation,
the server would crash when rolling back that transaction.

trx_commit_low(): Relax a too strict transaction. This function
will also be called after completing the rollback of a recovered
transaction.

trx_purge_add_undo_to_history(): Merged from the functions
trx_purge_add_update_undo_to_history() and trx_undo_update_cleanup(),
which are removed. Remove the parameter undo_page, and instead call
trx_undo_set_state_at_finish() to obtain it.

trx_write_serialisation_history(): Treat undo and old_insert equally.
That is, after the rollback (or XA COMMIT) of a recovered transaction
before upgrade, move all logs (both insert_undo and update_undo) to
the purge queue.