Instrumentations changing the HTTP route should respect context path

[sissbruecker]

Currently all instrumentations that modify the HTTP route, and the root span name, only use the route template. When deploying the application with a context path, for example /demo-app, then the root span name does not contain the full URL, and there is a mismatch with traces instrumented by other libraries (Servlet, Tomcat) that contain the context path.

At least the root span name should also contain the context path. For the http.route attribute it's arguable whether it should contain the context path, personally I'm leaning towards no.