Analyze the removal of ProxiedApiRouteEndpointLookup in favor of better use of endpoint routing

[joaofbantunes]

With ASP.NET Core 3.0, there seems to be more focus on endpoint routing (introduced in 2.2).

I haven't really looked at it much, but it might be worth it, to check if we can get rid of the manual routing we're doing with the ProxiedApiRouteEndpointLookup, in favor of using the routing capabilities already present in the framework.

As an example, we can take a look at what MapControllers does, see what we can learn from it.