fix: wait for HTTP server serve() termination

[rogercoll]

Fixes #347

[codecov]

Codecov Report

Attention: Patch coverage is 65.00000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 78.22%. Comparing base (2ecac8d) to head (372361f).

Files with missing lines	Patch %	Lines
server/serverimpl.go	65.00%	6 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #348      +/-   ##
==========================================
- Coverage   78.29%   78.22%   -0.07%     
==========================================
  Files          25       25              
  Lines        2386     2402      +16     
==========================================
+ Hits         1868     1879      +11     
- Misses        410      414       +4     
- Partials      108      109       +1     

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[tigrannajaryan]

This needs to honour ctx cancellation. If context is Done(), Stop() needs to return with an error. I am not sure if this is going to be the behavior, given that Wait() can wait indefinitely long. Please add a test that verifies the cancellation case.

[rogercoll]

Makes sense to me, added in 4e4986f

[tigrannajaryan]

Please update doc-comment of OpAMPServer.Stop() to explain that it waits until the server socket is released.

[rogercoll]

looks like there is an unrelated flaky test on the examples:
2025/02/13 14:49:28.332879 [OPAMP] Could not load TLS config, working without TLS: open ../../certs/certs/ca.cert.pem: no such file or directory

[rogercoll]

related data race issue #256

[tigrannajaryan]

related data race issue #256

I rerun the build a couple times and it fails. Perhaps this PR changed timings and the race is now encountered more consistently. Regardless of the reason I can't merge the PR if the build does not pass. We need to fix #256 first.