Removing constraints is always safe so there is no reason to block it on
compressed hypertables. Adding constraints is still blocked for
compressed hypertables as verifying of constraints currently requires
decompressed hypertable.
This patch changes those functions to no longer error by default when
the chunk is not the expected state, instead a warning is raised.
This is in preparation for changing compress_chunk to forward to
the appropriate operation depending on the chunk state.
This patch drops the catalog table _timescaledb_catalog.hypertable_compression
and stores those settings in _timescaledb_catalog.compression_settings instead.
The storage format is changed and the new table will have 1 entry per relation
instead of 1 entry per column and has no dependancy on hypertables.
All other aspects of compression will remain the same. This is refactoring is
to enable per chunk compression settings in a follow-up patch.
