Based on b/338409557#comment5, we update the onefingerpan toggle's
summary, and make the magnification settings page's footer HTML
description be dynamic based on one finger panning preference state.
Bug: 338409557
Flag: com.android.server.accessibility.enable_magnification_one_finger_panning_gesture
Test: manually
atest MagnificationOneFingerPanningPreferenceControllerTest
atest ToggleScreenMagnificationPreferenceFragmentTest
atest ToggleFeaturePreferenceFragmentTest
Change-Id: I817cad4fb0c034bcd2db0485ca27c30ea88a0280
Like MagnificationAlwaysOn toggle behavior, when the magnification
capability is window-mode only we'll hide the OneFingerPan toggle too.
Also do a small refactoring in MagnificationOneFingerPanningPreferenceControllerTest
Bug: 333821725
Flag: ACONFIG com.android.server.accessibility.enable_magnification_one_finger_panning_gesture TEAMFOOD
Test: manually
atest MagnificationOneFingerPanningPreferenceControllerTest
atest ToggleScreenMagnificationPreferenceFragmentTest
Change-Id: I8684b5bae5cbfc5b75fc4c14d2e9173b17d0fb02