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

tests/ModelContextProtocol.Tests/Client/McpClientCreationTests.cs

@@ -63,21 +63,20 @@ public class McpClientCreationTests
         {
             Capabilities = new ClientCapabilities
             {
-                Sampling = new SamplingCapability
-                {
-                    SamplingHandler = async (c, p, t) =>
-                        new CreateMessageResult 
-                        { 
-                            Content = new TextContentBlock { Text = "result" }, 
-                            Model = "test-model", 
-                            Role = Role.User, 
-                            StopReason = "endTurn" 
-                        },
-                },
                 Roots = new RootsCapability
                 {
                     ListChanged = true,
-                    RootsHandler = async (t, r) => new ListRootsResult { Roots = [] },
+                }
+            },
+            Handlers = new()
+            {
+                RootsHandler = async (t, r) => new ListRootsResult { Roots = [] },
+                SamplingHandler = async (c, p, t) => new CreateMessageResult
+                {
+                    Content = new TextContentBlock { Text = "result" },
+                    Model = "test-model",
+                    Role = Role.User,
+                    StopReason = "endTurn"
                 }
             }
         };

tests/ModelContextProtocol.Tests/Client/McpClientTests.cs

@@ -331,7 +331,7 @@ public class McpClientTests : ClientServerTestBase
         int remainingProgress = TotalNotifications;
         TaskCompletionSource<bool> allProgressReceived = new(TaskCreationOptions.RunContinuationsAsynchronously);
 
-        Server.ServerOptions.Capabilities?.Tools?.ToolCollection?.Add(McpServerTool.Create(async (IProgress<ProgressNotificationValue> progress) =>
+        Server.ServerOptions.ToolCollection?.Add(McpServerTool.Create(async (IProgress<ProgressNotificationValue> progress) =>
         {
             for (int i = 0; i < TotalNotifications; i++)
             {