Igniter: Use qtpy modules instead of Qt

[iLLiCiTiT]

Brief description

Replaced usage of Qt.py module with qtpy in igniter.

Testing notes:

Igniter tools should work as usually.

• Login (to mongo) screen is shown
• Update dialog is visible

[ynbot]

Task linked: OP-4654 qtpy in igniter

[64qam]

After the login to mongo:

--- launching setup UI ...
Traceback (most recent call last):
  File "C:\Users\qam\pypeclub\OpenPype\igniter\install_dialog.py", line 351, in _on_run_btn_click
    self._run_openpype()
  File "C:\Users\qam\pypeclub\OpenPype\igniter\install_dialog.py", line 378, in _run_openpype
    install_thread = InstallThread(self)
  File "C:\Users\qam\pypeclub\OpenPype\igniter\install_thread.py", line 38, in __init__
    super().__init__(self, parent)
TypeError: QThread() takes at most 1 argument (2 given)

[iLLiCiTiT]

After the login to mongo:

Should be fixed