cmd: group and move functions in test command

[KaloyanTanev]

Simple refactoring and grouping of the functions in the charon test files. They grew quite a lot and thought some grouping would help. There is nothing new introduced (except comments), despite git's assumption of many additions and deletions.

category: refactor
ticket: none

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
6.3% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

Attention: Patch coverage is 42.80303% with 302 lines in your changes missing coverage. Please review.

Project coverage is 57.73%. Comparing base (245f821) to head (27421c0).
Report is 1 commits behind head on kalo/test-command-ux.

Files with missing lines	Patch %	Lines
cmd/testpeers.go	61.31%	99 Missing and 19 partials ⚠️
cmd/testperformance.go	21.67%	101 Missing and 11 partials ⚠️
cmd/testbeacon.go	4.44%	43 Missing ⚠️
cmd/testvalidator.go	0.00%	19 Missing ⚠️
cmd/testmev.go	37.50%	9 Missing and 1 partial ⚠️

Additional details and impacted files

@@                   Coverage Diff                    @@
##           kalo/test-command-ux    #3377      +/-   ##
========================================================
- Coverage                 57.78%   57.73%   -0.05%     
========================================================
  Files                       217      217              
  Lines                     31619    31619              
========================================================
- Hits                      18270    18256      -14     
- Misses                    11467    11481      +14     
  Partials                   1882     1882              

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