SSTable compression parameters should always define an algorithm via the
`sstable_compression` sub-option. Add a check in the constructor to
ensure this is always provided (unless no options are given, which is
interpreted as "no compression").
This change has no user-visible effect, since the same check is already
performed at a higher-level, while validating the CQL properties of
CREATE TABLE and ALTER TABLE statements (see `cf_prop_defs::validate()`).
However, it will become useful in later patches, when compression config
options will be introduced.
Although now redundant, keep the sanity check in
`cf_prop_defs::validate()` to maintain consistency of error messages
with Cassandra.
Note also that Cassandra uses 'class' instead of 'sstable_compression'
since version 3.11.10, but Scylla still doesn't support this, see:
https://github.com/scylladb/scylladb/issues/4200
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>