Emit schema url from instrumentations

[trask]

Is your feature request related to a problem? Please describe.

Currently none of the instrumentations emit schema url, which makes it harder for backends to detect which version of semantic conventions are being emitted (in particular relevant for old vs stable semconv like HTTP, and soon Database).

Describe the solution you'd like

Emit the appropriate schema url from each instrumentation

Describe alternatives you've considered

No response

Additional context

No response