HTTP semantic convention / `OTEL_SEMCONV_STABILITY_OPT_IN` prototypes

[trask]

Based on open-telemetry/opentelemetry-specification#3241, we need at least three prototypes before we can mark HTTP semantic conventions as stable.

So far these prototypes exist (and are continuing to be updated) in Java and .NET.

[trask]

Update on prototyping requirement:

Java HTTP instrumentation was previously updated to 1.21.0. It is currently being updated to 1.22.0 and beyond (cc @mateuszrzeszutek).

.NET is in similar situation. HTTP instrumentation was previously updated to 1.21.0 and is currently being updated to 1.22.0 and beyond (cc @vishweshbankwar).

Python prototyping is underway (cc @lzchen)

• Requests instrumentation http semantic convention migration opentelemetry-python-contrib#2002

[trask]

Update on prototyping requirement:

Java - stable semantic conventions close to production ready across 23 HTTP client instrumentations and 11 HTTP server instrumentations (open-telemetry/opentelemetry-java-instrumentation#9785)

.NET - stable semantic conventions close to production ready for .NET HttpClient instrumentation and ASP.NET server instrumentation

Python - Basic prototype of one HTTP client instrumentation and two HTTP server instrumentations

[trask]

Closing, I believe the prototype requirement has been met (and produced the desired validation and feedback loop which resulted in several subsequent changes to the semantic conventions)