[Refactor] Remove Dashboard Agent service

[kevin85421]

Why are these changes needed?

Without #1173, the Kubernetes service for the dashboard agent uses a round-robin algorithm to evenly distribute traffic among the available Pods, including the head Pod and worker Pods. This may cause stability issues. Hence, #1173 decides to only send the requests to the head service's 52365 (dashboard agent port). The dashboard agent service is no longer used after #1173, so this PR aims to remove the service.

pod.go

1. Merge setAgentListPortStartParams into setMissingRayStartParams: The function setAgentListPortStartParams will always be called after setMissingRayStartParams and both have very similar functionalities. Hence, there is no reason to keep them as two separate functions.

2. Remove RayClusterDashboardServiceLabelKey: utils.GenerateDashboardAgentLabel(rayClusterName) from Pod labels. The label is for the dashboard agent service's selector.

Related issue number

#1173

Checks

• I've made sure the tests are passing.
• Testing Strategy
  • Unit tests
  • Manual tests
  • This PR is not tested :(

RAY_IMAGE=rayproject/ray:2.5.0 OPERATOR_IMAGE=controller:latest pytest -vs tests/test_sample_rayservice_yamls.py --log-cli-level=INFO