- Remove IStartupLoader and add `IStartup` instead that matches the signature hosting cares about
- Moved `UseStartup` to extension methods
- Move existing logic into `ConventionBasedStartup` class
- This change removes the indirection and between the IServerLoader and
the IServerFactory. We now add the IServerFactory directly to the DI
container and resolve it from there.
- Moved logic that resolves IServerFactory from an assembly to a static
helper