Terminate Beyla if we can't open a configured Prometheus port

[grcevski]

Beyla can fail to register the HTTP Prometheus metrics endpoint because of number of reasons. It can be that the port is already opened or we don't have permission to listen on a specific port.

Currently, when we fail to open the Prometheus port the Beyla process prints an error message, but then successfully runs. Successful run can be misleading, since for the end users there is no indication that the process is unhealthy and the error message is buried in the very first few lines of the logs. The symptom is metrics are not scraped, but Beyla is up and running.

This PR causes Beyla to terminate as soon as we fail to register the port. We can't add early validation for this error scenario, because we can't predict all of the possible reasons we may not be able to open the Prometheus port.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 81.98%. Comparing base (a3ffb2f) to head (b5a83f5).
Report is 1 commits behind head on main.

Files	Patch %	Lines
pkg/internal/connector/prommgr.go	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1111      +/-   ##
==========================================
- Coverage   82.03%   81.98%   -0.06%     
==========================================
  Files         140      140              
  Lines       11514    11517       +3     
==========================================
- Hits         9446     9442       -4     
- Misses       1548     1551       +3     
- Partials      520      524       +4     

Flag	Coverage Δ
integration-test	57.10% <20.00%> (-0.17%)	⬇️
k8s-integration-test	59.17% <20.00%> (-0.11%)	⬇️
oats-test	37.06% <0.00%> (-0.01%)	⬇️
unittests	52.33% <60.00%> (-0.04%)	⬇️

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[mariomac]

Good catch 🚀