Add support for Redis usernames in Workhorse and KAS config

What does this MR do?

Previously if the default username were disabled on Redis and a custom Redis ACL user were used, Workhorse and KAS would fail to connect with a WRONGPASS error.

This commits adds the username to the URL if it is available.

Related issues

Relates to #5681 (closed)

Testing

I created a separate Redis deployment:

redis-deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: redis
spec:
  replicas: 1
  selector:
    matchLabels:
      app: redis
  template:
    metadata:
      labels:
        app: redis
    spec:
      containers:
      - name: redis
        image: redis:latest
        ports:
        - containerPort: 6379
        env:
        - name: REDIS_PASSWORD
          value: "<password from gitlab-redis-secret secret>"
        command:
        - sh
        - -c
        - |
          echo "user default off >${REDIS_PASSWORD} ~* +@all allchannels" > /tmp/redis.conf
          echo "user redis-user on >${REDIS_PASSWORD} ~* +@all" >> /tmp/redis.conf
          redis-server /tmp/redis.conf
---
apiVersion: v1
kind: Service
metadata:
  name: redis
spec:
  ports:
  - port: 6379
    targetPort: 6379
  selector:
    app: redis

Then I ran:

kubectl apply -f redis-deployment.yaml

My values.yaml:

global:
  redis:
    auth:
      enabled: true
    user: redis-user
    connectTimeout: 3
    host: redis.default.svc.cluster.local
redis:
  install: false

Check that:

1. sidekiq, webservice, and kas pods start up.
2. In the webservice pod, the gitlab-workhorse container contains the username in /srv/gitlab/config/workhorse-config.toml in URL.

Author checklist

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Required

For anything in this list which will not be completed, please provide a reason in the MR discussion.

• Merge Request Title and Description are up to date, accurate, and descriptive.
• MR targeting the appropriate branch.
• MR has a green pipeline.
• Documentation created/updated.
• Tests added/updated, and test plan for scenarios not covered by automated tests.
• Equivalent MR/issue for omnibus-gitlab opened.

Reviewers checklist

• MR has a green pipeline on https://gitlab.com/gitlab-org/charts/gitlab.
• Consider downstream impact to the Operator, as per evaluating impact from changes to GitLab Chart.