Migrate kafka-operator to use lb-operator for exposing brokers

[nightkr]

Description

This is far from final (for example, we'd need to expose a configurable
LoadBalancerClass, for example), but I wanted to see whether lb-op would be a
good fit for this operator first.

Review Checklist

• Code contains useful comments
• CRD change approved (or not applicable)
• (Integration-)Test cases added (or not applicable)
• Documentation added (or not applicable)
• Changelog updated (or not applicable)
• Cargo.toml only contains references to git tags (not specific commits or branches)
• Helm chart can be installed and deployed operator works (or not applicable)

Once the review is done, comment bors r+ (or bors merge) to merge. Further information

[nightkr]

Blocked on stackabletech/listener-operator#1

[maltesander]

Tested and works!

[lfrancke]

I've moved this back into "Ready for Development" because the Listener operator is now merged. AFAIU this should now be ready to be worked on again?

[siegfriedweber]

I've moved this back into "Ready for Development" because the Listener operator is now merged. AFAIU this should now be ready to be worked on again?

This pull request is updated as requested by stackabletech/listener-operator#5. When stackabletech/operator-rs#496 is merged and operator-rs and the listener-operator are released then this pull request can be made ready for review.

[nightkr]

Tests currently fail due to stackabletech/listener-operator#110.

[nightkr]

The tests now pass!

[sbernauer]

@nightkr do you plan to merge this or add the WIP functionality of secret-op beforehand, so that the kafka broker certificates will include the listener addresses?
It'd be awesome if we get it right in the first run :)

[nightkr]

Preferably not, since we're still working out a few API kinks there (truststore passwords), and I'd rather keep this PR focused. ^^