[processor/interval] Create the initial structure for the new processor

[RichieSams]

Description:
Adds a new processor that aggregates metrics and periodically forwards the latest values to the next component in the pipeline.

NOTE: As per the CONTRIBUTING.md recommendations, this PR only creates the basic structure of the processor. The concrete implementation will come as a separate followup PR

Link to tracking Issue:
#29461

Testing:
This is just the basic structure, so no tests yet, other than the auto-generated ones for metadata.yaml

Documentation:

This adds the basic README, but more will be added in the followup PR which adds the concrete implementation

[djaglowski]

@RichieSams, looks like the collector modules need updating again. Feel free to ping me to restart CI

[RichieSams]

@djaglowski There are failing CI checks, but it looks to be all go.mod version mismatch issues. I keep rebasing to HEAD, but versions are changing faster than I can rebase and re-test. :(

How do you suggest we proceed?

[RichieSams]

@djaglowski I think we're good now to re-trigger CI. 🤞

[djaglowski]

@RichieSams, apologies for the churn here. I think we got unlucky trying to do this while a release is being cut. Still, we cannot merge without passing all required checks. I've restarted CI.

[RichieSams]

@djaglowski One of the checks if failing because my metadata.yml doesn't have values in the stability section:

2024/01/25 20:53:29 failed loading /home/runner/work/opentelemetry-collector-contrib/opentelemetry-collector-contrib/processor/intervalprocessor/metadata.yaml: missing stability

I removed that section though, because another check wants to make sure that the component exists in components.go. But according to the CONTRIBUTING.md we don't add that until it's "ready".

Can you assist?

[djaglowski]

@RichieSams, I think we need the stability section and it's ok for the component to be in components.go. I couldn't find the language you're referring to, regarding it being "ready", but I suspect it's out of date.

[RichieSams]

Ah, I may have been confused about some of the language here: https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/CONTRIBUTING.md#adding-new-components

I also didn't realize there is a development stability. So I used that. I think this should be good then.

[RichieSams]

Thanks for helping get it in! I'm working on the implementation. Initial PR probably tomorrow or next week

[songy23]

This broke mainline, seems a bad merge https://github.com/open-telemetry/opentelemetry-collector-contrib/actions/runs/7662556481/job/20884054028

[djaglowski]

Fixed by #30790. Thanks @mwear!