Add an IndexedTableLoader Extension

[suneet-s]

Create an extension that can load an IndexedTable from a provided
IndexIngestionSpec

The extension attemps to load the IngestionSpec on startup and reads the rows
into an RowBasedIndexedTable

This change makes the LifecycleLock non final for easier testing

Follow up patches:

• Hook up the RowBasedIndexTable to a DataSource so that it can be queried
• Refactor the RowBasedIndexTable to accept a row so that it can load the
  index table in just one pass over the rows
• Introduce an IndexedTableResource so that the tables can be loaded via an
  API instead of just through config
• Refactor the IngestionSpec so that any spec can provide an iterator over
  the input source. This will allow the extension to read the IndexedTable from
  any format.

This PR has:

• been self-reviewed.
  • using the concurrency checklist (Remove this item if the PR doesn't have any relation to concurrency.)
• added documentation for new or modified features or behaviors.
• added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• added or updated version, license, or notice information in licenses.yaml
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths.
• added integration tests.
• been tested in a test Druid cluster.