Register first lookup immediately, regardless of the cache status.

[pranavbhole]

Description

In case of the first version of the lookup, we can skip waiting for initialization where it is good or bad configuration and just load it as it is. Esp for MSQ workers, it get spin off for each tasks, and issues loadNotice with no previous lookup version.
For first lookup, it get registered immediately regardless of the cache status. For subsequent version of the lookup, we make sure that new lookup come up before we kill the existing good lookup.

In subsequent version of the same lookup, we always make sure that we wait until new lookup config is loaded with cache before we kill the old working lookup.

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.
• a release note entry in the PR description.
• 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, ensuring the threshold for code coverage is met.
• added integration tests.
• been tested in a test Druid cluster.

[soumyava]

LGTM

[vogievetsky]

hmm why did the bot add a web console label?

[abhishekrb19]

hmm why did the bot add a web console label?

@vogievetsky, my guess is that a web-console file was touched in one of the earlier commits and removed in a later commit. The auto-labeler bot config has sync-labels turned off by default because we noticed it'd otherwise spuriously remove labels manually added by maintainers. So the sync feature is turned off by default and folks need to remove irrelevant labels manually when the scope of a PR changes.

(It'll be nice if auto-labeler bot syncs only bot-added labels with sync-labels = true, but oh well, it doesn't exist :))