Localize the removal of root tasks to default TDA in tests

- Change the implementation of removeRootTaskWithActivityTypes test
  API such that the removal only happens on default TDA.
- As there could be safety critical activities running in other TDAs
- Problem with removing those activities is that they cannot be
  reliably restarted in a way where all CTS remain fine.

Flag: EXEMPT (Test only)
Bug: 205581941
Test: Ran all WM CTS modules on a device having activities in
      additional TDAs
Change-Id: Ib1710348b19ae1a81b6228f9788db067dde08a3f