[chore] (processor/transformprocessor) migrate feature gates to metadata.yaml

[agarvin-nr]

Description

• Adds feature gate section to metadata.yaml with processor.transform.ConvertBetweenSumAndGaugeMetricContext and transform.flatten.logs
• Adds reference URL and from_version feature gate information to processor.transform.ConvertBetweenSumAndGaugeMetricContext
• Removes manual feature gate registration
• Generated metadata

Link to tracking issue

Part of #46116

Testing

• go build ./..., make gotest and make golint all pass

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: agarvin-nr / name: Ansen Garvin (7f70a8c, b2204a2, f746f05)

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[evan-bradley]

Hi @agarvin-nr, thanks for helping us migrate this. The processor.transform.ConvertBetweenSumAndGaugeMetricContext feature gate is being removed here, so you can remove it from this PR since we'll no longer need it.

[agarvin-nr]

Hi @agarvin-nr, thanks for helping us migrate this. The processor.transform.ConvertBetweenSumAndGaugeMetricContext feature gate is being removed here, so you can remove it from this PR since we'll no longer need it.

Hi @evan-bradley, I just removed it! While migrating other components, if I come across similar long-since-stable and unused feature gates, should I remove them as well or is it best to do so on a case-by-case basis?

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[mx-psi]

@agarvin-nr It looks like there was anotehr feature gate that can be moved on this component, see

opentelemetry-collector-contrib/processor/transformprocessor/factory.go

Lines 37 to 45 in 371d54d

	const defaultErrorModeIgnoreGateID = "processor.transform.defaultErrorModeIgnore"
	var defaultErrorModeIgnoreFeatureGate = featuregate.GlobalRegistry().MustRegister(
	defaultErrorModeIgnoreGateID,
	featuregate.StageAlpha,
	featuregate.WithRegisterDescription("Changes the default error_mode of the transform processor from propagate to ignore"),
	featuregate.WithRegisterReferenceURL("https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/47231"),
	featuregate.WithRegisterFromVersion("v0.150.0"),
	)

If you want to open a PR to remove this one I think that would allow us to remove this linter rule

opentelemetry-collector-contrib/.golangci.yml

Lines 206 to 208 in 208b7c0

	- linters:
	- forbidigo
	path: processor/transformprocessor/

:)

[agarvin-nr]

@mx-psi Sure thing! I just made a PR for it #47542 . I didn't know that linter rule was a thing for feature gates, that's cool! I went ahead and removed that exclusion as a part of the same PR, I hope that's alright.