Quantum Gateway device tracker tests (#145161)

* move constants to central const file

* add none return type to device scanner constructor

* add quantum gateway device tracker tests

* fix

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Co-authored-by: Joostlek <joostlek@outlook.com>

CODEOWNERS

@@ -1228,6 +1228,7 @@ build.json @home-assistant/supervisor
 /homeassistant/components/qnap_qsw/ @Noltari
 /tests/components/qnap_qsw/ @Noltari
 /homeassistant/components/quantum_gateway/ @cisasteelersfan
+/tests/components/quantum_gateway/ @cisasteelersfan
 /homeassistant/components/qvr_pro/ @oblogic7
 /homeassistant/components/qwikswitch/ @kellerza
 /tests/components/qwikswitch/ @kellerza