Fix OBI being blocked on shutdown

[mariomac]

Summary

OBI is taking long to exit, mainly because the OpenTelemetry metrics exporters got blocked during their Shutdown. This PR takes a best-effort approach to OTEL metrics shutdown: we try to shut it down in a background goroutine, as it is not a critical operation (the worst case is that we loose few last data points in an OBI instance we are anyway shutting down).

The approach that was taken to fix it in the integration tests was to wrap the OBI process into a shell script, but that was hiding the blocking in production, and its real cause.

It also broke the coverage reporting of the integration tests, as the OBI process was killed before it had time to exit.

This should also fix this issue: #781

Validation

• I have read and followed the contributing guidelines
• If this enhances / fixes / changes a core feature, I have updated the features documentation

[codecov]

Codecov Report

❌ Patch coverage is 44.82759% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.20%. Comparing base (7d92c2f) to head (7eb72e8).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...rnal/test/integration/components/docker/compose.go	0.00%	8 Missing ⚠️
pkg/internal/appolly/appolly.go	37.50%	4 Missing and 1 partial ⚠️
pkg/export/otel/metrics_svc_graph.go	66.66%	2 Missing ⚠️
pkg/export/otel/metrics.go	83.33%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1782       +/-   ##
===========================================
+ Coverage   45.06%   60.20%   +15.13%     
===========================================
  Files         339      339               
  Lines       37481    37489        +8     
===========================================
+ Hits        16892    22571     +5679     
+ Misses      19518    13749     -5769     
- Partials     1071     1169       +98     

Flag	Coverage Δ
integration-test	57.16% <66.66%> (+35.92%)	⬆️
integration-test-arm	30.03% <42.85%> (+30.03%)	⬆️
integration-test-vm-x86_64-5.15.152	31.05% <44.44%> (+31.05%)	⬆️
integration-test-vm-x86_64-6.10.6	30.08% <44.44%> (+30.08%)	⬆️
k8s-integration-test	43.90% <66.66%> (+41.79%)	⬆️
oats-test	38.04% <66.66%> (+38.04%)	⬆️
unittests	48.58% <30.76%> (-0.01%)	⬇️

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[grcevski]

LGTM! Nice! I was seeing these a lot on my new hardware.

[mmat11]

thanks for fixing this!