Restart kernel initial implementation (#18835)

* Restart kernel initial implementation

* Update notebook extension TestKernel

* PR comments

extensions/notebook/src/jupyter/jupyterKernel.ts

@@ -109,6 +109,10 @@ export class JupyterKernel implements nb.IKernel {
 	interrupt(): Promise<void> {
 		return this.kernelImpl.interrupt();
 	}
+
+	restart(): Promise<void> {
+		return this.kernelImpl.restart();
+	}
 }
 
 export class JupyterFuture implements nb.IFuture {

extensions/notebook/src/test/common.ts

@@ -308,6 +308,9 @@ export class TestKernel implements azdata.nb.IKernel {
 	interrupt(): Thenable<void> {
 		throw new Error('Method not implemented.');
 	}
+	restart(): Thenable<void> {
+		throw new Error('Method not implemented.');
+	}
 }
 //#endregion