Editor file picker can be pinned/unpinned
This feature would add a button toggle to file picker to alternate the behavior of the file picker to either have its current behavior or (new) to be docked and always visible on the left hand side of the debugger.
- Pin toggle added to the right of the input box for the file picker
- Toggle is 2nd in tab order (after the input box) for the file picker
- Width of the pane will be resizable and persisted
- When docked, the file picker items are added to the tab order of the debugger (the tree as one control)