Remove the innodb_undo suite, and move and adapt the tests.
Remove unnecessary restarts, and add innodb_page_size_small.inc
for combinations.

innodb.undo_truncate is the merge of innodb_undo.truncate
and innodb_undo.truncate_multi_client.

Add the global status variable innodb_undo_truncations.
Without this, the test innodb.undo_truncate would occasionally
report that truncation did not happen. The test was only waiting
for the history list length to reach 0, but the undo tablespace
truncation would only take place some time after that.

Undo tablespace truncation will only occasionally occur with
innodb_page_size=32k, and typically never occur (with this amount
of undo log operations) with innodb_page_size=64k. We disable
these combinations.

innodb.undo_truncate_recover was formerly called
innodb_undo.truncate_recover.