Implement merging of Resources with different schemas in resourcedetectionprocessor

[tigrannajaryan]

resourcedetectionprocessor modifies the Resources that pass through it by merging it with the Resources
it detected. This merging is valid when the schemas of the original Resource and the merged Resource
are the same, but it is generally speaking incorrect when the schemas are different.

Proposed OTEP 0161 defines how Resources of different schemas can be merged correctly by leveraging
schema conversion capabilities:
https://github.com/open-telemetry/oteps/blob/b2cb1558c6fa88535ef68f7a19df147a1b6fc162/text/0161-telemetry-schema-and-resource.md#resource-merge-logic

Once we have a code that implements schema conversion we can use it in resourcedetectionprocessor's
MergeSchemaURL/MergeResource functions.

[github-actions]

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[tigrannajaryan]

Depends on #5036

[github-actions]

This issue has been inactive for 60 days. It will be closed in 60 days if there is no activity. To ping code owners by adding a component label, see Adding Labels via Comments, or if you are unsure of which component this issue relates to, please ping @open-telemetry/collector-contrib-triagers. If this issue is still relevant, please ping the code owners or leave a comment explaining why it is still relevant. Otherwise, please close it.

[tigrannajaryan]

This is waiting for OTEP 0161 and for schema processor implementation.

[github-actions]

Pinging code owners for processor/resourcedetection: @Aneurysm9 @dashpole. See Adding Labels via Comments if you do not have permissions to add labels yourself.

[wafer-bw]

For those following the frustrating saga of "conflicting Schema URL" error covered by issues such as open-telemetry/opentelemetry-go#4476, open-telemetry/opentelemetry-go-contrib#4261, etc...

It is my understanding that OTEP-0161 mentioned by @tigrannajaryan here was lost when oteps were moved to the new specification repo here.

At this time, as far as I can tell, otel packages still do not follow conventional semantic versioning. Run-time breaking changes can and will be introduced in MINOR releases via the semconv.SchemaURL as documented by resource.Merge):

If the resources have different, non-empty, schema URLs an error containing ErrSchemaURLConflict will be returned with the merged Resource. The merged Resource will have an empty schema URL. It may be the case that some unintended attributes have been overwritten or old semantic conventions persisted in the returned Resource. It is up to the caller to determine if this returned Resource should be used or not.

We can see that the resource.SchemaURL documentation does not reflect the proposed changes in OTEP-0161.

Given that this issue was last updated years ago it is unclear to me what, if anything, is being done to resolve this issue.