Mock WheelsV2 in unit-tests to avoid lengthy wheel-building. (#2281)

## Changes

This PR updates some of the unit-testing fixtures to mock `WheelsV2`
where this is referenced instead of the real thing; this avoids lengthy
wheel-building during unit tests.

(Wheel-building can easily exceed the 30s unit-testing deadline,
especially on developer laptops with the solacc dataset present.)

Author: asnare

tests/unit/install/test_install_dashboards.py

@@ -1,5 +1,6 @@
 import logging
 from datetime import timedelta
+from unittest import mock
 
 import pytest
 from databricks.labs.blueprint.installation import MockInstallation
@@ -23,7 +24,7 @@
 def workspace_installation(request, ws, any_prompt) -> WorkspaceInstallation:
     mock_installation = request.param if hasattr(request, "param") else MockInstallation()
     install_state = InstallState.from_installation(mock_installation)
-    wheels = WheelsV2(mock_installation, PRODUCT_INFO)
+    wheels = mock.create_autospec(WheelsV2)
     workflows_installation = WorkflowsDeployment(
         WorkspaceConfig(inventory_database="..."),
         mock_installation,