[CI] Upgrade otel-webserver-module CI to opentelemetry-cpp 1.15.0

[marcalff]

Upgrade otel-webserver-module CI to opentelemetry-cpp 1.15.0.

If possible, please use semantic conventions from opentelemetry-cpp, instead of local constants such as:

const std::string kServiceName = "service.name";

as found in SdkConstants.h.

See opentelemetry-cpp header file opentelemetry/sdk/resource/semantic_conventions.h

https://github.com/open-telemetry/opentelemetry-cpp/blob/main/sdk/include/opentelemetry/sdk/resource/semantic_conventions.h

[aryanishan1001]

I will look into it and make the required changes.