feat: add service monitor to redis sentinel chart

[drivebyer]

Description

Fixes #1042

Type of change

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

Checklist

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

Additional Context

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.67%. Comparing base (d121d86) to head (6ef9c3d).
Report is 104 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1071       +/-   ##
===========================================
+ Coverage   35.20%   45.67%   +10.47%     
===========================================
  Files          19       20        +1     
  Lines        3213     2704      -509     
===========================================
+ Hits         1131     1235      +104     
+ Misses       2015     1387      -628     
- Partials       67       82       +15     

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