Hide auto-generated cell in ipynb workflows (#1574)

## Changes

Using the same metadata that web UI sets when you click on "hide code"
option for a cell.

It looks like this, and the cell can be expanded by clicking on the eye
button (after which you can't hide it anymore)
<img width="991" alt="Screenshot 2025-02-25 at 15 31 09"
src="https://github.com/user-attachments/assets/15029782-f4ee-4405-a3ba-e3cc322a8bad"
/>



Dbnb notebooks will still have the generated cells visible.



## Tests

Manually + existing integ tests

Author: ilia-db

packages/databricks-vscode/scripts/writeIpynbWrapper.ts

@@ -14,7 +14,11 @@ interface INbCell {
 const nbCell: INbCell = {
     cell_type: "code",
     source: [],
-    metadata: {},
+    metadata: {
+        jupyter: {
+            source_hidden: true,
+        },
+    },
     outputs: [],
     execution_count: null,
 };