Checks if the document imports PySide and whether the selected python
interpreter can find a PySide installation. If not show a global info
bar that can install PySide via pip like the python lsp server.
Task-number: PYSIDE-1742
Change-Id: I02c0d5f6eb268f3d8826d4fb9d9ec3c7c48b8638
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
