rcu: Remove rcutorture test version and sequence number

Back when RCU had a debugfs interface, there was a test version and
sequence number that allowed associating debugfs data with a particular
test run, where the test run started with modprobe and ended with rmmod,
which was how tests were run back on the old ABAT system within IBM.
But rcutorture testing no longer runs on ABAT, and there is no longer an
RCU debugfs interface, so there is no longer any need for test versions
and sequence numbers.

This commit therefore removes the rcutorture_record_test_transition()
and rcutorture_record_progress() functions, and along with them the
rcutorture_testseq and rcutorture_vernum variables that they update.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>