KAFKA-7588: Pass custom configs to the ChannelBuilder implementations

[omkreddy]

This PR ensures we provide custom configs to ChannelBuilder implementations apart from config.values() we pass currently.

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[rajinisivaram]

@omkreddy Thanks for the PR, LGTM
@mimaison Since you raised the JIRA, can you also review this PR please?

[rajinisivaram]

@omkreddy Since @mimaison hasn't responded, I will merge this to trunk. If there are additional comments, we can address them in a follow-on PR.

[mimaison]

Sorry I meant to take a look!
Are there any pluggable APIs left that don't get custom configs?

[omkreddy]

@mimaison This covers all below listed security related pluggable interfaces. looks like for all other interfaces, we already passing all original configs.

• principal.builder.class
• sasl.login.callback.handler.class
• sasl.login.class
• sasl.server.callback.handler.class
• sasl.client.callback.handler.class
• security.providers