.. share->last_version' failed in myisam/mi_open.c:67: test_if_reopen

During the RENAME operation since the renamed temporary table is also
opened and added to myisam_open_list/maria_open_list, resetting the
last_version at the end of operation (HA_EXTRA_PREPARE_FOR_RENAME)
will cause an assertion failure when a subsequent query tries to open
an additional temporary table instance and thus attempts to reuse it
from the open table list.

This commit fixes the issue by skipping flush/close operations executed
toward the end of ALTER for temporary tables. It also enables a shortcut
for simple ALTERs (like rename, disable/enable keys) on temporary
tables.

As safety checks, added some assertions at code points that should not
be hit for temporary tables.