Remove UseServer overloads

[davidfowl]

We're moving away from generic hosting understanding how to wire up servers to servers adding themselves to the DI container via first class extension methods. This also avoids issues where the default extension methods setup things by default (like a default set of options) so that it's possible to configure server settings in the application.

[muratg]

This would be a breaking change, right? So in RC2? Could you start a thread for approval?

cc @Eilon @DamianEdwards

[Eilon]

What exactly do we want to remove/change? And are these APIs already frequently used?

[muratg]

Let's revisit after RC2.

[Tratcher]

Fowler's latest ask: Remove the extension, the config value, and the server factory that read the server value. Require servers be registered via DI in Main.