Support running WMShellUnitTests from studio

- Remove unnecessary @Presubmit annotation
- Fix issue with test activity referencing wrong resources
- Disable protolog requirement for tests when running under studio
  (like we do for SysUI studio builds)
- Ensure all tests extend ShellTestCase

Test: Run tests from studio, and also from atest WMShellUnitTests
Bug: 238444377
Change-Id: I60a96dfcbbf119d6736e96193f5a7d41611e2fd1