cmd: test command file output improvements

[KaloyanTanev]

Couple of small improvements over the test command:

• Swap TOML with JSON file on output
• Change the file format to include all 5 categories, so commands like test all can successfully write all results to the file
• Safe write to the file (using temp file)
• Put the MEV create block tests under a --load-test flag, so we don't put external infra under excess in the default case

An some small fixes that have been missed:

• Rename the testperformance file to testinfra
• Add the beacon node simulations file directory for results as a flag

category: refactor
ticket: none

[codecov]

Codecov Report

Attention: Patch coverage is 69.56522% with 21 lines in your changes missing coverage. Please review.

Project coverage is 57.35%. Comparing base (81563b9) to head (48be92d).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/test.go	56.25%	15 Missing and 6 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3384      +/-   ##
==========================================
+ Coverage   57.33%   57.35%   +0.01%     
==========================================
  Files         217      217              
  Lines       31915    31964      +49     
==========================================
+ Hits        18300    18332      +32     
- Misses      11727    11736       +9     
- Partials     1888     1896       +8     

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[sonarcloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
21.4% Duplication on New Code

See analysis details on SonarQube Cloud