admin check enhancement

## Enhancement
`ADMIN CHECK DATA/INDEX` checks against only data and index only. It's nice if it can also extend to check the table metadata, like the auto incremental id next_val etc.

Start by locating the implementation and tests for the ADMIN CHECK DATA/INDEX command, then trace how it checks data and indexes. Determine how table metadata such as the auto-increment id next_val is represented and what inconsistencies should be reported; done means the command also checks the requested metadata with coverage for its behavior.

Written by the indexing model from the issue text.