Decouple Handlers and Collections from protocol types (#765)

* Decouple Handlers and Collections (e.g. ToolsHandler and ToolsCollection) from Capabilities by promoting them to the options types.

Also, group all handlers in container classes, for server, I decided to move McpServerHandlers down to Mcp.Core and move the NotificationHandlers there too.

Also, Fix ListResourceTemplatesHandler issue.

* Add remarks for empty protocol capability types

* Keep JsonIgnore properties and mark them as Obsolete

* Continue supporting Obsolete members

* Update Obsolete messages to indicate the member will be removed

* Add EditorBrowsable Never to the remaining obsolete members

docs/concepts/elicitation/samples/client/Program.cs

@@ -18,12 +18,9 @@ McpClientOptions options = new()
         Name = "ElicitationClient",
         Version = "1.0.0"
     },
-    Capabilities = new()
+    Handlers = new()
     {
-        Elicitation = new()
-        {
-            ElicitationHandler = HandleElicitationAsync
-        }
+        ElicitationHandler = HandleElicitationAsync
     }
 };