tests: Add unit test for off-strategy sstable compaction
tests: Add unit test for off-strategy sstable compaction

Signed-off-by: Raphael S. Carvalho <1e2942cea40e3b4d2162dfcd9e53e41c05a84d22@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla