cmd: add custom number of validators beacon simulation test

[KaloyanTanev]

• Add a custom number of validators beacon simulation test, so users can test for their specific scenario.
• Fix some test names inconsistencies
• Improve the charon test all UX - print results to terminal after all tests complete
• Add missed MEV load test check
• Move the test command out of alpha state 🎉

category: feature ticket: none

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 57.39645% with 72 lines in your changes missing coverage. Please review.

Project coverage is 57.30%. Comparing base (eba4d33) to head (8122ad1). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/testbeacon.go	53.03%	31 Missing :warning:
cmd/testall.go	0.00%	23 Missing :warning:
cmd/cmd.go	0.00%	8 Missing :warning:
cmd/testpeers.go	78.94%	4 Missing :warning:
cmd/testinfra.go	88.88%	2 Missing :warning:
cmd/testmev.go	90.47%	2 Missing :warning:
cmd/testvalidator.go	85.71%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #3385 +/- ## ========================================== - Coverage 57.34% 57.30% -0.05% ========================================== Files 217 217 Lines 31964 32028 +64 ========================================== + Hits 18330 18353 +23 - Misses 11740 11781 +41 Partials 1894 1894 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[sonarcloud[bot]]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

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

See analysis details on SonarQube Cloud