[ISSUE #8182] Modify variable names to enhance readability #8182

[Stephanie0002]

Which Issue(s) This PR Fixes

Fixes #8182

Brief Description

Change the variable name 'group' to 'subGroup' and change the variable name 'subscription' to 'subExpression'

How Did You Test This Change?

Start namesvr and broker, set namesvr in the code, set parameters, then run producer and consumer, run well, and the message can be sent and consumed

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 42.85%. Comparing base (dcc88c6) to head (fe5f73f).

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #8183      +/-   ##
=============================================
- Coverage      42.91%   42.85%   -0.06%     
+ Complexity     10373    10362      -11     
=============================================
  Files           1270     1270              
  Lines          88723    88723              
  Branches       11405    11405              
=============================================
- Hits           38073    38026      -47     
- Misses         45947    45989      +42     
- Partials        4703     4708       +5     

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