add additional check to nginxProcesses

[aphralG]

Proposed changes

Add additional check to nginxProcesses to check process cmd has prefix of nginx:

Move if statement used to check processes to a separate function to add unit tests

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• I have run make install-tools and have attached any dependency changes to this pull request
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• If applicable, I have updated any relevant documentation (README.md)
• If applicable, I have tested my cross-platform changes on Ubuntu 22, Redhat 8, SUSE 15 and FreeBSD 13

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[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (ab97ac9) 66.23% compared to head (d77226b) 66.29%.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #483      +/-   ##
==========================================
+ Coverage   66.23%   66.29%   +0.06%     
==========================================
  Files         118      118              
  Lines       13441    13443       +2     
==========================================
+ Hits         8902     8912      +10     
+ Misses       3944     3938       -6     
+ Partials      595      593       -2     

Files	Coverage Δ
src/core/environment.go	51.16% <66.66%> (+0.14%)	⬆️

... and 2 files with indirect coverage changes

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