Verify if the http.server.request.duration includes time to read the request payload.

[vishweshbankwar]

[TimothyMothra]

Goal is to make sure "what is measured" is clearly documented on the official docs:
https://learn.microsoft.com/en-us/dotnet/core/diagnostics/built-in-metrics-aspnetcore?view=aspnetcore-8.0#metric-httpserverrequestduration

Currently this is:

The time used to handle an inbound HTTP request as measured at the hosting layer of ASP.NET Core. The time measurement starts once the underlying web host has:

- Sufficiently parsed the HTTP request headers on the inbound network stream to identify the new request.
- Initialized the context data structures such as the [HttpContext](https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.http.httpcontext).

The time ends when:

- The ASP.NET Core handler pipeline is finished executing.
- All response data has been sent.
- The context data structures for the request are being disposed.