feat: update PeriodicExportingMetricReader and PrometheusExporter to accept optional metric producers

[aabmass]

Which problem is this PR solving?

Part of #3461

Short description of the changes

Updated PeriodicExportingMetricReader and PrometheusExporter to accept optional metricProducers and pass them onto the superclass MetricReader constructor.

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

This is a simple config change, but I tested them both manually.

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• Documentation has been updated

[codecov]

Codecov Report

Merging #4077 (319ccb3) into main (0cc9a0b) will not change coverage.
The diff coverage is n/a.

❗ Current head 319ccb3 differs from pull request most recent head a5182ba. Consider uploading reports for the commit a5182ba to get more accurate results

Additional details and impacted files

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  Coverage   92.37%   92.37%           
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  Files         321      321           
  Lines        9276     9276           
  Branches     1970     1970           
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  Hits         8569     8569           
  Misses        707      707           

Files Changed	Coverage Δ
...etry-exporter-prometheus/src/PrometheusExporter.ts	96.25% <ø> (ø)
...etrics/src/export/PeriodicExportingMetricReader.ts	92.98% <ø> (ø)

[dyladan]

Looks good just one question. Why would the MetricProducer return a Resource if it is just going to be ignored? Is it used somewhere else?

[aabmass]

Why would the MetricProducer return a Resource if it is just going to be ignored? Is it used somewhere else?

We had a previous discussion about this #4007 (comment). The initial reason was to re-use the existing MetricProducer as is, which already had this signature. The existing MetricProducer is used by the SDK in MetricReader.setMetricProducer().

• Since it's marked experimental, we could introduce a new interface for "external" MetricProducers that doesn't include Resource.
• We could accept a Resource parameter to produce() (as described in MetricProducer.Produce can include a Resource parameter opentelemetry-specification#3636) but that would also require changing the existing interface or introducing a new one
• We could leave it as is

[aabmass]

Could a maintainer merge this in?