Support creating indexes on metadata schema fields

Automatically create a B-Tree database index on metadata schema field and make sure it is used in queries that check for range of values.

Start by locating the metadata schema field creation path and the queries that check ranges of values. Trace how schema changes and metadata searches are handled before deciding where index creation belongs. Done means B-Tree indexes are automatically created for metadata schema fields and range queries use them.

Written by the indexing model from the issue text.