feat: add self-observability metrics to otlpmetricgrpc metric exporters

[minimAluminiumalism]

Fixes #7012

• Added internal/selfobservability package to gRPC exporters
• Implemented three metrics as per OpenTelemetry SDK metrics specification:
  • otel.sdk.exporter.metric_data_point.inflight (UpDownCounter)
  • otel.sdk.exporter.metric_data_point.exported (Counter)
  • otel.sdk.exporter.operation.duration (Histogram)

[codecov]

Codecov Report

❌ Patch coverage is 92.10526% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.9%. Comparing base (c09be18) to head (894c26c).

Files with missing lines	Patch %	Lines
...pc/internal/selfobservability/selfobservability.go	89.3%	9 Missing and 3 partials ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##            main   #7120    +/-   ##
======================================
  Coverage   82.9%   82.9%            
======================================
  Files        264     266     +2     
  Lines      24628   24779   +151     
======================================
+ Hits       20425   20561   +136     
- Misses      3820    3832    +12     
- Partials     383     386     +3     

Files with missing lines	Coverage Δ
...porters/otlp/otlpmetric/otlpmetricgrpc/exporter.go	85.8% <100.0%> (+2.8%)	⬆️
...ers/otlp/otlpmetric/otlpmetricgrpc/internal/x/x.go	100.0% <100.0%> (ø)
...pc/internal/selfobservability/selfobservability.go	89.3% <89.3%> (ø)

... and 2 files with indirect coverage changes

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[minimAluminiumalism]

@pellared I've tried to fix the CI pipeline failures, please review this PR and re-trigger the pipeline check.

[pellared]

@minimAluminiumalism, can you please make the documentation and changelog entry similar to other modules? You can take a look at #7121 for another reference.

[minimAluminiumalism]

@minimAluminiumalism, can you please make the documentation and changelog entry similar to other modules? You can take a look at #7121 for another reference.

The changelog and doc.go have been modified.

[flc1125]

Since this PR includes 2 components, I suggest implementing one of them first, as it will be easier to get through during both implementation and review.

[flc1125]

As a supplementary note (which might be useful), when conducting unit tests for metrics, we can use this package: https://github.com/open-telemetry/opentelemetry-go/tree/main/sdk/metric/metricdata/metricdatatest

In fact, I haven't started the review of unit tests yet. (Reason: The functional part has not yet been fully reviewed).

[minimAluminiumalism]

Since this PR includes 2 components, I suggest implementing one of them first, as it will be easier to get through during both implementation and review.

I've removed the implementation of otlpmetrichttp, please review it.

[flc1125]

The functional components have been largely reviewed, and unit testing has not yet commenced.

[flc1125]

The functional part is basically in line with expectations, requiring only minor adjustments.

[flc1125]

Review based on unit testing

[flc1125]

Thank you for your contribution.

[minimAluminiumalism]

@pellared @flc1125 I've fixed the CI pipeline falilures caused by docs, please re-run it.

[minimAluminiumalism]

@flc1125 Conflicts resolved, re-run the pipeline please :)

[minimAluminiumalism]

@flc1125 Maybe it's time to merge this PR? I'll implement it of otlpmetrichttp next.

[flc1125]

@flc1125 Maybe it's time to merge this PR? I'll implement it of otlpmetrichttp next.

Sorry, I was on vacation last week, and there have been some significant recent changes that I need to review.

[flc1125]

Please use this component https://github.com/open-telemetry/opentelemetry-go/tree/main/exporters/stdout/stdouttrace as a reference; there have been some recent optimizations, and we need to adjust accordingly.

You can view the change log via this link: https://github.com/open-telemetry/opentelemetry-go/commits/main/exporters/stdout/stdouttrace

Please refer to the adjustment for this range: 2ab7d4d...c2a6172

[pellared]

@minimAluminiumalism PTAL #7272

[minimAluminiumalism]

@pellared @flc1125 Apologies for the delay—I’ve been blocked by other priorities and will aim to complete this PR by next week.

[flc1125]

Hi, since this process involves specification adjustments and historical review records (which may contain invalid review suggestions), it’s impossible to tell which items need attention amid the large volume of information.

Could we create a new PR based on the current branch before preparing for the review, so that subsequent reviews can proceed more smoothly?

Thanks~