Fix DB bugs and improvements

[r2dedios]

Describe the bug
There are several things to fix in the DB schema

Additional context

1. Bug: instances.cluster_id is an INTEGER but it refers to clusters.id which is BIGINT
2. Bug: events.resource_id is an INTEGER but clusters.id and instances.id are BIGINT
3. Not using RESOURCE_TYPE in events table nor its CHECK statement
4. Logical Bug: cluster_tags omits repeated tags but HAVING COUNT(*) > 1 does the opposite