Closes #231298

Changes

2. Introduced ExplorerResourceParentReadOnlyContext to track whether or not the parent of the selected explorer item is read only.
3. Updated the preconditions of createNewFile and createNewFolder.

Testing

1. Select a file nested in a readonly directory. The create-new-file and create-new- folder buttons will be grey and unclickable. (This is aligned with the actual behavior of the buttons when clicked. Previously they were clickable but did nothing.)
2. Select a readonly file in a writable directory. The buttons will not be grey, they will be clickable.
3. Select a readonly directory. The buttons will be grey and unclickable.