[cleanup][client] Remove unnecessary pause/resume logic from MultiTopicsConsumerImpl and cleanup putIfAbsent logic

[lhotari]

Motivation

Cleanup code in MultiTopicsConsumerImpl.

• The pause/resume logic is unnecessary that was added in [client] Optimize pause when creating sub consumers in multi-topic consumer #14566. The only necessary change would be to set configurationData.setStartPaused(paused)
• The putIfAbsent logic is not optimal since the new consumer is first created and then closed if there's a duplicate
• The logic for putIfAbsent handling was missing in another location

Modifications

• cleanup pause/resume logic for internal consumers
• cleanup and replace the putIfAbsent logic

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

[codecov-commenter]

Codecov Report

❌ Patch coverage is 62.96296% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.33%. Comparing base (807dcaf) to head (ae28a15).

Files with missing lines	Patch %	Lines
...he/pulsar/client/impl/MultiTopicsConsumerImpl.java	62.96%	8 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #25009      +/-   ##
============================================
+ Coverage     74.27%   74.33%   +0.06%     
- Complexity    33563    34078     +515     
============================================
  Files          1920     1920              
  Lines        150279   150263      -16     
  Branches      17448    17447       -1     
============================================
+ Hits         111618   111699      +81     
+ Misses        29768    29656     -112     
- Partials       8893     8908      +15     

Flag	Coverage Δ
inttests	26.39% <33.33%> (?)
systests	22.87% <14.81%> (+0.02%)	⬆️
unittests	73.86% <62.96%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...he/pulsar/client/impl/MultiTopicsConsumerImpl.java	76.36% <62.96%> (-0.65%)	⬇️

... and 99 files with indirect coverage changes

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