Listener support/external access

[nightkr]

Description

Fixes #174, supersedes #175.

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

# Tasks before R4R
- [x] Support external access
- [x] Support Kerberos
- [ ] https://github.com/stackabletech/docker-images/pull/506
- [x] Move listenerclass into role config? https://stackable-workspace.slack.com/archives/C02FZ581UCD/p1704714818413279
- [ ] Add proper listener watch for discovery
- [x] Docs
- [ ] Tests

# Author
- [ ] Changes are OpenShift compatible
- [x] CRD changes approved
- [x] CRD documentation for all fields, following the [style guide](https://docs.stackable.tech/home/nightly/contributor/style-guide).
- [x] Helm chart can be installed and deployed operator works
- [x] Integration tests passed (for non trivial changes)
- [x] Changes need to be "offline" compatible

# Reviewer
- [x] Code contains useful comments
- [x] (Integration-)Test cases added
- [x] Documentation added or updated. Follows the [style guide](https://docs.stackable.tech/home/nightly/contributor/style-guide).
- [x] Changelog updated
- [x] Cargo.toml only contains references to git tags (not specific commits or branches)

# Acceptance
- [ ] Feature Tracker has been updated
- [ ] Proper release label has been added

[soenkeliebau]

Should we close #175 to avoid confusion?

[nightkr]

Sounds good yeah.

[nightkr]

Watching is blocked on stackabletech/listener-operator#138, but I wouldn't block on that since most expected changes here would be during startup/scale events (which would ping the operator anyway).

We'd still want to pull that out into an issue here and fix eventually, obviously.

[nightkr]

The current testing approach is blocked on kudobuilder/kuttl#322. Are we okay to punt on testing external access as long as the internal access tests still function?