Includes:
MDEV-17302 Add support for ALTER USER command in prepared statement
and
MDEV-17673 main.cte_recursive fails in bb-10.4-ps branch in --ps
Set correct SELECT_LEX linkage for recursive CTEs.
Do not delegate this job to TABLE_LIST::set_as_with_table,
because it is only run on prepare, while With_element::move_anchors_ahead
is run both on prepare and execute (fix by Igor)
The reason is that selecting from events_waits_history_long creates
a race condition: it can happen that SHOW EXPLAIN thread was kicked
off CPU exactly after posting a SHOW EXPLAIN request and then it wont
need to wait.
It doesn't seem to make sense to add more waits to stabilize the testcase.
Let's instead make a check that SHOW EXPLAIN statement has a
"stage/sql/show explain" stage.
