feat: add redis-role label to redis replication

[drivebyer]

Description

Fixes #765

Type of change

• New feature (non-breaking change which adds functionality)

Checklist

• [x] Tests have been added/modified and all tests pass.
• [x] Functionality/bugs have been confirmed to be unchanged or fixed.
• [x] I have performed a self-review of my own code.
• [ ] Documentation has been updated or added where necessary.

Additional Context

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 49 lines in your changes are missing coverage. Please review.

Project coverage is 39.08%. Comparing base (d121d86) to head (50f4458). Report is 45 commits behind head on master.

Files	Patch %	Lines
k8sutils/pod.go	0.00%	26 Missing :warning:
controllers/redisreplication_controller.go	0.00%	21 Missing :warning:
k8sutils/labels.go	0.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #925 +/- ## ========================================== + Coverage 35.20% 39.08% +3.88% ========================================== Files 19 20 +1 Lines 3213 2720 -493 ========================================== - Hits 1131 1063 -68 + Misses 2015 1586 -429 - Partials 67 71 +4 ```

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