CorruptedSSTablesCompactionsTest is flaky

See e.g. this run.

The test was looked at for CASSANDRA-15879, but it is still failing from time to time. One of the failures appears to be introduced by CASSANDRA-14227 and the others by CASSANDRA-18134. The failures are genuine problems with handling corruption, not just test issues.

The CorruptSSTableException paths in SSTableIdentityIterator should likely also catch AssertionError and IllegalArgumentException, and most probably the tombstone verification should be done on the read path.