[mdatagen] Consider linking metrics/attributes from metadata.yaml to SemConv definitions

[ChrsMark]

mdatagen allows today to set sem_conv_version within the metdata.yaml file. However this version is only used to import the semantic conventions module at

opentelemetry-collector/cmd/mdatagen/internal/templates/metrics.go.tmpl

Line 311 in 4ca0f18

rm.SetSchemaUrl(conventions.SchemaURL)

Currently, there is no way for us to know if metrics defined in metadata.yaml follow the Semantic Conventions or not. We should consider linking metrics defined in metadata.yaml to their Semantic Convnetions' definitions, if exist.

This should be similar to how SchemaUrl is defined:

opentelemetry-collector/cmd/mdatagen/internal/templates/metrics.go.tmpl

Line 311 in 4ca0f18

rm.SetSchemaUrl(conventions.SchemaURL)

This will allow us to:

1. Leverage Semantic Conventions definitions directly where exist
2. Generated code will use imported conventions' metric names directly
3. Define per metric/attribute stability level directly from SemConv
4. Start using stable semantic conventions in components: hostmetricsreceiver semantic conventions transition opentelemetry-collector-contrib#35325
5. Help with components' stability discussions: Document SemConv compatibility requirements for components stability #11878

[mx-psi]

This makes sense to me, I support doing this

[ChrsMark]

note: I'd be happy to work on this after August unless somebody else want to tackle it earlier