[occm] Add support for x-forwarded-port and x-forwarded-proto annotations

[huhji-elha]

What this PR does / why we need it:

This PR adds support for the x-forwarded-port and x-forwarded-proto Service annotations in cloud-provider-openstack (OCCM).

OCCM already supports x-forwarded-for to preserve the client IP address.
This change extends the existing functionality to also propagate the original client port and protocol to backend services, using Octavia listener insert_headers.

The change is fully backward compatible and includes test code and documentation updates.

Which issue this PR fixes(if applicable):
fixes #3034

Special notes for reviewers:

• This PR is split into multiple commits for easier review:

  • Feature implementation: add x-forwarded-port and x-forwarded-proto annotations
  • Test updates: add loadbalancer test for x-forwarded-*
  • Documentation updates: docs: add x-forwarded-port and x-forwarded-proto annotations

• Existing behavior is preserved unless the new annotations are explicitly enabled.

• Some small refactoring is included to keep the listener and pool protocol selection logic consistent and easier to reason about.

Release note:

[openstack-cloud-controller-manager] Add support for `x-forwarded-port` and `x-forwarded-proto` Service annotations when using Octavia.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: huhji-elha / name: El-ha! (10dc18f, 222bffc, 3cc63d8)

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[kayrus]

/ok-to-test