Enable Cumulative to Delta Processor

[dmitrykruglov]

Description:

Enabling Cumulative to Delta processor which would allow for converting cumulative monotonic metrics to delta metrics.

Link to Splunk idea: https://ideas.splunk.com/ideas/SFXIMMID-I-599

Testing:

• Has been tested with a splunk-otel-collector helm chart (w/ a custom-built image) deployed in an EKS cluster, with the "cumulativetodelta" processor enabled in the processors config, and the processor added to the "metrics" pipeline like so:

metrics:
  processors:
  - memory_limiter
  - cumulativetodelta
  - k8sattributes/metrics
  - batch
  - resourcedetection
  - resource

We have confirmed that the metrics values that used to be ever-increasing monotonic numbers have become deltas as a result.

• Unit tests pass

Documentation: I've updated the list of components doc to include the cumulativetodelta processor (as part of this PR).

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[dmitrykruglov]

I have read the CLA Document and I hereby sign the CLA

[crobert-1]

It would be good to add an entry in CHANGELOG.md for this, under a new components header. Link for an example.

[dmitrykruglov]

Thank you all for the review. I've just updated the changelog as well.