SettingsGoogle: Add ContextualScreenTimeout

Store contextual screen timeout preference when the
corresponding switch is toggled.

Bug: 295232527

Test: atest ExternalSettingsProviderTest
Test: atest ContextualTimeoutPreferenceControllerTest
Change-Id: Ib3707e5e47f10f36d4e1d807a9977dacaaa894a5
3 files changed