Move opentelemetry-semconv version management to opentelemetry-bom

Is your feature request related to a problem?

It is about general dependency management hygiene and logical organization of it: what do you think about moving semconv's (io.opentelemetry.semconv/opentelemetry-semconv) dependency management from opentelemetry-instrumentation-bom to opentelemetry-bom?

From user perspective, opentelemetry-semconv should be next to opentelemetry-api (BOM-wise) since they are providing OTel "~interfaces" and both can be used without the Java instrumentation. This would also help making semconv more loosely coupled (one of OTel's core values) since right now, (logically/BOM-wise) it is a bit more coupled to instrumentation since it is in that BOM.

Describe the solution you'd like

Moving semconv's dependency management to opentelemetry-bom. Right now it is in opentelemetry-instrumentation-bom (see here) and semconv is used by users without instrumentation.

Describe alternatives you've considered

Not sure there is much, there are only two places for it, the current and opentelemetry-bom that I think is a better fit.

Additional context

I think this would not be a breaking change for users since opentelemetry-instrumentation-bom brings in opentelemetry-bom.

Start with bom/build.gradle.kts at the referenced dependency-management block, then inspect the opentelemetry-bom and opentelemetry-instrumentation-bom definitions. Verify how the two BOMs are composed and run the relevant Gradle build or dependency-management checks. Done means semconv is managed by opentelemetry-bom while instrumentation users retain the expected dependency resolution.