Populate OTel Schema URL on HTTP Activity Sources and Meters

[lmolkova]

SchemaURL support is being introduced in #113034, we should set it on ActivitySources and Meters created by HTTP client and related libs (see all sources and HTTP meter)

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[antonfirsov]

What should be the value of the schema Url? Should it point to an actual schema file? Who is responsible for owning/hosting/maintaining the schema?

Are we aware of .NET customer scenarios important for 10.0?

[KalleOlaviNiemitalo]

Is it going to be just https://opentelemetry.io/schemas/1.30.0, to indicate that Semantic Conventions 1.30.0 for HTTP are used?

[antonfirsov]

The .NET implementation goes beyond the standard, see https://github.com/open-telemetry/semantic-conventions/blob/main/docs/dotnet/dotnet-http-metrics.md and open-telemetry/semantic-conventions#1192.