[fix][fn] Go functions need to use static grpcPort in k8s runtime

[flowchartsman]

Fixes apache#20403

Motivation

Allow Go pulsar functions to respond to the function worker for status requests.

Modifications

Make KubernetesRuntimeFactory assign static grpcPort instead of a random available port, so that the pod will respond correctly to status requests.

Verifying this change

• Make sure that the change passes the CI checks.

This change is a trivial rework / code cleanup without any test coverage. I didn't see any tests for this, but if needed I can add them.

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository: TBD for full PR