feat: rolling update sequence from leader to follower

[drivebyer]

Description

Fixes #951

Type of change

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

Checklist

• [x] Tests have been added/modified and all tests pass.
• [ ] 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 33 lines in your changes missing coverage. Please review.

Project coverage is 40.69%. Comparing base (d121d86) to head (e89777d). Report is 65 commits behind head on master.

:exclamation: Current head e89777d differs from pull request most recent head 9125951

Please upload reports for the commit 9125951 to get more accurate results.

Files	Patch %	Lines
k8sutils/statefulset.go	0.00%	29 Missing :warning:
controllers/rediscluster_controller.go	0.00%	3 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #966 +/- ## ========================================== + Coverage 35.20% 40.69% +5.49% ========================================== Files 19 20 +1 Lines 3213 2703 -510 ========================================== - Hits 1131 1100 -31 + Misses 2015 1532 -483 - Partials 67 71 +4 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[wkd-woo]

Great !