Move Magnification Mode Settings to the main page

We move the mode settings because currently there is
only one item in the settings page. To fully test all logic,
we don't use fragament anymore in the controllerTest, and
test the interaction between the controller and the fragment
in the test of these two fragments.

Bug: 182992338
Test: atest ToggleScreenMagnificationPreferenceFragmentTest
      atest MagnificationModePreferenceControllerTest
      atest MagnificationSettingsFragmentTest
      manually test
Change-Id: Ia6b0ea4f116f3215407637d7aeaddb8d8196d8fb