[adamtheturtle]

Nine shared query test modules required the concrete mock database type even though they only sign requests or pass credentials to shared query helpers. Accept CloudDatabaseCredentials throughout these tests, preserving the requests, assertions and backend parametrization. The query directory now has no direct mock_vws imports.

Towards #3738.

Depends on #3786, including the shared retry repair from #3794, and targets its branch.

Validation:

• Existing shared query tests: 162 passed, 81 skipped in 53.63s.
• Pre-commit and pre-push hooks passed, including partition checks and all type checkers, on the updated tree.
• git diff --check passed.

No test cases or dependencies were added. Hosted CI for the updated head is pending.