Imported the following tests from Oracle MySQL:

* mysql-test/t/locking_clause.test
* mysql-test/suite/innodb/t/skip_locked_nowait.test
* mysql-test/t/locking_part.test

Ported to MariaDB by Daniel Black, changes include:
* Removed 'FOR SHARE OF /FOR UPDATE OF' tests that are part of
  MDEV-17514 (not yet implemented)
* mysql-test/t/locking_clause.test removes broken the limit test (outstanding MDEV-25244) bug.
* mysql-test/suite/innodb/t/skip_locked_nowait.test - removed high
  priority transactions
* mysql-test/t/locking_part.test imported to mysql-test/suite/innodb/t/partition_locking.test
  changed ER_LOCK_NOWAIT -> ER_LOCK_WAIT_TIMEOUT consistent with already
  implemented WAIT/NOWAIT feature. Changed "FOR SHARE SKIP LOCKED" ->
  "LOCK IN SHARE MODE SKIP LOCKED".