Summary: Metadata server uses pebble db if the appropriate flag is set.

Test Plan: Manual testing

Reviewers: michelle, nserrino, vihang, #engineering

Reviewed By: vihang, #engineering

JIRA Issues: PP-2478

Differential Revision: https://phab.corp.pixielabs.ai/D7517

GitOrigin-RevId: 3cb06225f5aef73edf8284640a62059160f247c2