Add "inserted" metrics to processors

[djaglowski]

Link to tracking issue

Resolves #10353

Testing

Added equivalent testing to other processor metrics (accepted, refused, dropped).

Documentation

Metric documentation is autogenerated.

Open Question

My initial implementation includes a breaking change to componenttest.TestTelemetry which is public facing API. If we want to avoid an immediate breaking change in this test package, I would propose the following, which I can submit in a prerequisite PR:

1. Deprecate all TestTelemetry.Check* methods.
2. Replace with more granular TestTelemetry.CheckOneSpecificMetric methods.

[codecov]

Codecov Report

Attention: Patch coverage is 89.09091% with 6 lines in your changes missing coverage. Please review.

Project coverage is 92.56%. Comparing base (0d6e6bf) to head (0716a03).
Report is 12 commits behind head on main.

❗ Current head 0716a03 differs from pull request most recent head b4bcc9f

Please upload reports for the commit b4bcc9f to get more accurate results.

Files	Patch %	Lines
component/componenttest/obsreporttest.go	0.00%	6 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #10372   +/-   ##
=======================================
  Coverage   92.56%   92.56%           
=======================================
  Files         387      387           
  Lines       18254    18297   +43     
=======================================
+ Hits        16896    16937   +41     
- Misses       1014     1015    +1     
- Partials      344      345    +1     

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[mx-psi]

I am okay with breaking API in one go, but the breaking change should appear in the API changelog.

I am not sure if there is any overlap with open-telemetry/oteps/pull/259 (I guess not in terms of the metric names, but possibly on the namespaces?). Is there a chance we would have to change these after that OTEP is finalized?

[djaglowski]

I am okay with breaking API in one go, but the breaking change should appear in the API changelog.

Thanks, I'll add a changelog - just wanted to agree on the direction before going further with it.

I am not sure if there is any overlap with open-telemetry/oteps/pull/259 (I guess not in terms of the metric names, but possibly on the namespaces?). Is there a chance we would have to change these after that OTEP is finalized?

I think there is overlap and if the otep is accepted we will need to make quite a few changes. However, my understanding of the proposal is that all of the counts we currently have for processors, as well as these "inserted" counts would be relevant, though they would be grouped with others into new metrics. I think regardless of this PR we may end up deprecating the current metrics in favor of a new set, but both could coexist for a while.

[mx-psi]

LGTM, will wait a few days in case others want to chime in