This patch introduces following modifications:
Disallows enabling cdc for table X when X_scylla_cdc_log already exists,
Restricts DROP permissions for X_scylla_cdc_log tables,
Restricts ALTER and DROP permissions for cdc_description and cdc_topology_description,
Disallows cdc option when creating materialized views.
Refs #4991.
Tests: unit(dev).
* piodul/4991-permissions-for-cdc-tables:
cdc: disallow CDC options for materialized views
cdc: restrict permissions on cdc_(topology_)description
cdc: restrict permissions on _scylla_cdc_log tables
cdc: refuse to enable cdc when table _scylla_cdc_log exists