diag.error about unknown OTEL_NODE_RESOURCE_DETECTORS entry should be diag.warn

[trentm]

opentelemetry-js/experimental/packages/opentelemetry-sdk-node/src/utils.ts

Lines 56 to 60 in 34003c9

	if (!resourceDetector) {
	diag.error(
	`Invalid resource detector "${detector}" specified in the environment variable OTEL_NODE_RESOURCE_DETECTORS`
	);
	}

Currently it is a diag.error, but I think it should be a diag.warn.

https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/configuration/sdk-environment-variables.md#enum-value says:

if the user provides a value the implementation does not recognize, the implementation MUST generate a warning and gracefully ignore the setting.

Originally posted by @trentm in #4879 (comment)

---

There is a similar diag.error in auto-instrumentations-node that I think should be a diag.warn as well:
https://github.com/open-telemetry/opentelemetry-js-contrib/blob/6e8989de4d60c32bc9b3e3ef760e92c68ae7f491/metapackages/auto-instrumentations-node/src/utils.ts#L280

[pichlermarc]

marking as bug/p4 (incorrect log level)