H*** Marry 2 kinds of reports: unused and redundant

TODO

• When presenting the list of redundant indexes, show usage information about every redundant index, collecting it from all nodes (the master and all its replicas).
• Fix logic of Redundant Indexes report:
  • compare index types / access methods (we must not suggest dropping gin index claiming that its redundant to btree and vice versa);
  • non of indexes are partial or they are both partial, with identical predicates;
  • to ensure, that index access methods match, and both of them or none of them have the Unique option;
  • if both indexes have Unique option, and one of them supports PK constraint, never suggest dropping it.

See also: https://gitlab.com/postgres-ai-team/postgres-health-check/issues/186

Acceptance criteria

As a DBA, I see is a redundant index being used or not, so I can conclude do I need to drop it.

Redundant indexes report doesn't detect PKs as "redundant" if identical (redundant) unique index is defined.

The report doesn't detect as redundant an index which is btree, while the other one is gin or of other type. And vice versa.

The report doesn't detect as redundant a partial index if the other index is not redundant or have different predicate. And vice versa.