[CLIENT-3805] Add missing app_id attribute to Cluster class for extended metrics

[DomPeliniAerospike]

Extra changes:

• Allow client config option app_id to be set to None.
• Document default value for client config's app_id and cluster_name option to be None.
• Update outdated documentation for client config's cluster_name option.

Docs

https://aerospike-python-client--864.org.readthedocs.build/en/864/aerospike.html#:~:text=meaning%20‘never%20compress’-,cluster_name,-(Optional[str

TODO

• cluster_name description needs to be tested
• app_id documentation needs improvement.

Manual testing

Valgrind run
Massif run
Build artifacts with tests
Code coverage is fully covered, coverage report shows missing lines because it is a standalone test.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 80.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.28%. Comparing base (50f5b0f) to head (de3a767).
⚠️ Report is 9 commits behind head on dev.

Files with missing lines	Patch %	Lines
src/main/conversions.c	77.77%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #864      +/-   ##
==========================================
+ Coverage   83.25%   83.28%   +0.03%     
==========================================
  Files          99       99              
  Lines       14348    14374      +26     
==========================================
+ Hits        11946    11972      +26     
  Misses       2402     2402              

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