feat: Rewrite Redis environment variables API

[AJIOB]

• Implement Redis configuration values splitting support
• Actualize Redis main docs
• Actualize configuration docs
• Use both old & new Redis API for tests

Fix #2083

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 66.66667% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 56.41%. Comparing base (0cc0c62) to head (9424a81).
Report is 4 commits behind head on main.

Files	Patch %	Lines
src/config.rs	66.66%	7 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2116       +/-   ##
===========================================
+ Coverage   30.91%   56.41%   +25.50%     
===========================================
  Files          53       53               
  Lines       20112    20338      +226     
  Branches     9755     9791       +36     
===========================================
+ Hits         6217    11474     +5257     
+ Misses       7922     7591      -331     
+ Partials     5973     1273     -4700     

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[Xuanwo]

Thanks a lot for the tests!