Discovery: Database metrics for KV store implementations

[N-o-Z]

Currently metrics are collected base on SQL statistics for the Postgres DB implementation. Some of these metrics are not relevant / impossible to obtain on different driver implementation. As such, we need to define per driver which statistics we want to collect from the database and create an appropriate interface to provider these statistics. For now, discussed with @ortz and agreed upon the following:

• For the meantime, Postrgres KV implementation will continue providing the current statistics as provided by the DB implementation
• DynamoDB - disable statistics

We should define the requirements for the stats under this issue and modify the current behavior for the drivers as necessary

[N-o-Z]

After discussion - decided to remove database statistics entirely from lakeFS

• #3893