Refactor transports to help enable graceful shutdown (#142)

- This also paves the way for better multi-session support
- We should definitely rethink names for the transport API
- For now, I kept the names similar as possible, so we can
  focus on the API shape

Co-authored-by: Stephen Toub <stoub@microsoft.com>

src/ModelContextProtocol/Client/McpClientFactory.cs

@@ -82,7 +82,14 @@ public static class McpClientFactory
         }
         catch
         {
-            await transport.DisposeAsync().ConfigureAwait(false);
+            if (transport is IAsyncDisposable asyncDisposableTransport)
+            {
+                await asyncDisposableTransport.DisposeAsync().ConfigureAwait(false);
+            }
+            else if (transport is IDisposable disposableTransport)
+            {
+                disposableTransport.Dispose();
+            }
             throw;
         }
     }