This will makes it easier to find out what replication workers are
doing and what they are waiting for.

Things changed in processlist:
- Slave_SQL time was not consistent. Now time for state "Slave has
  read all relay log; waiting for more updates" shows how long it has
  waited for getting the next event.
- Slave_worker threads did often show "Closing tables" for a long
  time.  Now the state is reverted to the previous state after
  "Closing tables" is done.
- Commit and Rollback states where not shown for replication (and some
  other threads). Now Commit and Rollback states are always shown and
  the state is reverted to previous state when the Commit/Rollback
  have finished.

Code changes:
- Added thd->set_time_for_next_stage() for parallel replication when
  when starting to wait for prior transactions to commit, group commit,
  and FTWRL and for free space in thread pool.
  Before we reset the time only after the above events.
- Moved THD_STAGE_INFO(stage_rollback) and THD_STAGE_INFO(stage_commit)
  from sql_parse.cc to transaction.cc to ensure this is done for
  all commits and not only 'normal connection queries'.

Test case changes:
- close_thread_tables() reverting stage to previous stage caused the
  counter in performance_schema to be increased. In many case it is
  the 'sql/starting' stage that was effected.
- We only change to "Commit" stage if there is a need for a commit.
  This caused some "Commit" stages to disapper from perfschema reports.

TODO in 11.#:
- Slave_IO always showes "Waiting for master to send event" and the time is
  from SLAVE START. We should in 11.# change this to be the time since
  reading the last event.