fix(tests): client_mocks moved inside the package, imports for tests adjusted

tests/unit_tests/test_device_initialization_progress_bar.py

@@ -2,12 +2,11 @@
 import pytest
 from bec_lib.messages import DeviceInitializationProgressMessage
 
+from bec_widgets.tests.client_mocks import mocked_client
 from bec_widgets.widgets.progress.device_initialization_progress_bar.device_initialization_progress_bar import (
     DeviceInitializationProgressBar,
 )
 
-from .client_mocks import mocked_client
-
 
 @pytest.fixture
 def progress_bar(qtbot, mocked_client):