[OpAMP.Client] Add heartbeats

[RassK]

Changes

Adds heartbeats to support http transport scenario.

There is no client side api yet to provide info about components etc. Only reports static heartbeats.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes

[codecov]

Codecov Report

❌ Patch coverage is 57.25806% with 53 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.02%. Comparing base (efa16d9) to head (f5637ed).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...OpenTelemetry.OpAmp.Client/Internal/OpAmpClient.cs	0.00%	14 Missing ⚠️
...penTelemetry.OpAmp.Client/Internal/FrameBuilder.cs	48.00%	13 Missing ⚠️
...nt/Internal/Services/Heartbeat/HeartbeatService.cs	77.55%	11 Missing ⚠️
...ternal/Services/Heartbeat/ComponentHealthStatus.cs	0.00%	9 Missing ⚠️
...Telemetry.OpAmp.Client/Internal/FrameDispatcher.cs	72.22%	5 Missing ⚠️
...pAmp.Client/Internal/Settings/HeartbeatSettings.cs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3095      +/-   ##
==========================================
+ Coverage   69.82%   70.02%   +0.20%     
==========================================
  Files         426      420       -6     
  Lines       16495    16559      +64     
==========================================
+ Hits        11517    11595      +78     
+ Misses       4978     4964      -14     

Flag	Coverage Δ
unittests-Instrumentation.Cassandra	?
unittests-OpAmp.Client	70.35% <57.25%> (-3.88%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...Client/Internal/Services/Heartbeat/HealthReport.cs	100.00% <100.00%> (ø)
...mp.Client/Internal/Settings/OpAmpClientSettings.cs	83.33% <100.00%> (ø)
...pAmp.Client/Internal/Settings/HeartbeatSettings.cs	50.00% <50.00%> (ø)
...Telemetry.OpAmp.Client/Internal/FrameDispatcher.cs	80.00% <72.22%> (+5.00%)	⬆️
...ternal/Services/Heartbeat/ComponentHealthStatus.cs	0.00% <0.00%> (ø)
...nt/Internal/Services/Heartbeat/HeartbeatService.cs	77.55% <77.55%> (ø)
...penTelemetry.OpAmp.Client/Internal/FrameBuilder.cs	64.44% <48.00%> (-20.56%)	⬇️
...OpenTelemetry.OpAmp.Client/Internal/OpAmpClient.cs	0.00% <0.00%> (ø)

... and 21 files with indirect coverage changes

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[Kielek]

Intentionally left for follow ups?

For now, all contrib packages are using EventSources similar to https://github.com/open-telemetry/opentelemetry-dotnet-contrib/blob/8452d88e83e1c204bd4b43c7c3d8189f94ff87be/src/OpenTelemetry.Resources.Host/HostResourceEventSource.cs

(There are even tests for it).

[RassK]

Yes, that was my plan as well. Will address logging in a separate PR.