Backport PR #12156: Export KernelConnection (#12167)

Co-authored-by: tkrabel-db <91616041+tkrabel-db@users.noreply.github.com>

packages/services/src/kernel/index.ts

@@ -5,6 +5,7 @@
 import * as Kernel from './kernel';
 import * as KernelMessage from './messages';
 import * as KernelAPI from './restapi';
+import { KernelConnection } from './default';
 
 export * from './manager';
-export { Kernel, KernelMessage, KernelAPI };
+export { Kernel, KernelMessage, KernelAPI, KernelConnection };