MDEV-18429: Simpler implementation

This reverts commit 61f370a
and implements a simpler fix that is straightforward to merge to 10.3.

lock_print_info: Renamed from PrintNotStarted. Dump the
entire contents of trx_sys->mysql_trx_list.

lock_print_info_rw_recovered: Like lock_print_info, but dump
only recovered transactions in trx_sys->rw_trx_list.

lock_print_info_all_transactions(): Dump both trx_sys->mysql_trx_list
and trx_sys->rw_trx_list.

TrxLockIterator, TrxListIterator, lock_rec_fetch_page(): Remove.
This is a partial backport of the 10.3
commit a447980
which removed the race-condition-prone ability of the InnoDB monitor
to read relevant pages into the buffer pool for some record locks.