[CCXDEV-14924] Remove Redis instance and old cache writer

[JiriPapousek]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Changes in REST API schema
• Refactor (refactoring code, removing useless files)
• Unit tests (no changes in the code)
• Behavioral tests (no changes in the code)
• REST API tests
• Bump-up dependent library (no changes in the code)
• Security fix in dependent library (no changes in the code)
• Security fix in dependent library (changes made in the code)
• Benchmarks (no changes in the code)
• Documentation update
• Configuration update

Testing steps

Please describe how the change was tested locally. If, for some reason, the testing was not done or not done fully, please describe what are the testing steps.

Checklist

• make before_commit passes
• updated documentation wherever necessary
• added or modified tests if necessary
• updated schemas and validators in insights-data-schemas in case of input/output change

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.90%. Comparing base (4753901) to head (bb723c5).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2192   +/-   ##
=======================================
  Coverage   71.90%   71.90%           
=======================================
  Files          80       80           
  Lines        7038     7038           
=======================================
  Hits         5061     5061           
  Misses       1621     1621           
  Partials      356      356           

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