Rework error handling to use OpenIdConnectMessage and update the samples accordingly

*OpenIdConnectRequestError extension methods have been replaced by
*OpenIdConnectMessage.
*OpenIdConnectMessage extension methods now store both the
OpenIdConnectMessage instance and the OIDC parameters in a untyped way.
OpenIdConnectServerHandler has been reworked to use
SendErrorRedirectAsync/SendErrorPageAsync and SendErrorPayloadAsync
massively.