PMM-12510: Replace getDiagnosticData for connection tests

[idoqo]

PMM-12510

Link to the Feature Build: SUBMODULES-3483

If this PR adds or removes or alters one or more API endpoints, please review and add or update the relevant API documents as well:

• API Docs updated

If this PR is related to some other PRs in this or other repositories, please provide links to those PRs:

• PMM-12510 correctly recognize arbiter nodes mongodb_exporter#755

[codecov]

Codecov Report

Attention: 22 lines in your changes are missing coverage. Please review.

Comparison is base (ce0fbe8) 42.00% compared to head (974cc49) 42.18%.
Report is 2 commits behind head on main.

Files	Patch %	Lines
agent/connectionchecker/connection_checker.go	62.96%	7 Missing and 3 partials ⚠️
agent/utils/version/mongo.go	47.05%	6 Missing and 3 partials ⚠️
agent/serviceinfobroker/service_info_broker.go	50.00%	1 Missing and 1 partial ⚠️
managed/services/agents/service_info_broker.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2754      +/-   ##
==========================================
+ Coverage   42.00%   42.18%   +0.17%     
==========================================
  Files         395      396       +1     
  Lines       50048    50077      +29     
==========================================
+ Hits        21023    21125     +102     
+ Misses      27025    26950      -75     
- Partials     2000     2002       +2     

Flag	Coverage Δ
agent	53.18% <56.25%> (+0.83%)	⬆️
managed	42.73% <0.00%> (ø)

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