Enable `HttpRequest.RequestContext`

## Summary

`HttpRequest.RequestContext` is similar to endpoint information. The information here may be able to be exposed in a way that makes this available to code written for System.Web.

## In scope

- `System.Web.HttpRequest.RequestContext`
- `System.Web.Routing.RouteData`
- `System.Web.Routing.IRouteHandler`
- `System.Web.Routing.RouteValueDictionary`

## Out of scope

- The System.Web routing system itself; this would just expose data with types from System.Web but gather it from endpoints

## Risks / unknowns

- This may start bringing in more than we'd want (especially around the namespace System.Web.Routing). This would need to be explored a bit more.