Deprecate opentracing-shim

[jack-berg]

OpenTracing is deprecated. We should mark the code in our opentelemetry-opentracing-shim as deprecated, and stop publishing sometime in 2027 per spec guidance: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/compatibility/opentracing.md#opentracing-compatibility

[ADITYA-CODE-SOURCE]

I’d like to work on this.
My plan is to deprecate the public opentracing-shim entrypoints and update the module documentation in line with the spec guidance, while keeping the scope limited to deprecation annotations and docs.