Add IHttpSysRequestTimingFeature to support accessing http.sys timing info

[NGloreous]

Adding IHttpSysRequestTimingFeature to support a well-defined type for accessing http.sys request timing info

Addresses a portion of #35012 by exposing a well-defined API to access http.sys timing info.

Description

Currently http.sys request info is exposed as a ROM via IHttpSysRequestInfoFeature in #14119. Now that the API has stabilized, we want to add well-defined APIs to expose this information. This PR adds APIs to access all timings, individual timings by type, and to get elapsed time between two timings.

The request timing information from http.sys provides high resolution timestamps, obtained from calling QueryPerformanceCounter, of the various steps of request processing. Exposing this information to the consuming service can be helpful in understanding the total time spent to process requests, attribute that time to the various stages of request processing, and diagnose issues when they arise.

Contributes to #35012

[ghost]

Thanks for your PR, @NGloreous. Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[amcasey]

Looks like

src/Servers/HttpSys/src/RequestProcessing/Request.cs(4,1): error IDE0005: Using directive is unnecessary.

[ghost]

@NGloreous, this change will be considered for inclusion in the blog post for the release it'll ship in. Nice work!

Please ensure that the original comment in this thread contains a clear explanation of what the change does, why it's important (what problem does it solve?), and, if relevant, include things like code samples and/or performance numbers.

This content may not be exactly what goes into the blog post, but it will help the team putting together the announcement.

Thanks!