CmdPal: Allow pinned top-level items to be displayed as a Grid

### Description of the new feature / enhancement

The pinned items on the home of the command palette could have a grid-like look which adjusts according to the number of pinned items on the palette.
A section could be dedicated to the palette extensions, which would also have a grid-like look

### Scenario when this would be used?

In the command palette utility

### Supporting information

_No response_

Start by inspecting the command palette home view and how pinned top-level items and palette extensions are currently rendered. Define the grid behavior for different numbers of pinned items and provide a dedicated grid-like section for extensions; the work is done when the layout adjusts correctly across those cases.

Written by the indexing model from the issue text.