Add the new Desktop Experience dev options

This option, when available, replaces the enable freeform ones.

Bug: 390625230
Bug: 389092752
Test: atest DesktopExperiencePreferenceControllerTest
Test: atest DesktopModeSecondaryDisplayPreferenceControllerTest
Test: atest DesktopModePreferenceControllerTest
Test: atest FreeformWindowsPreferenceControllerTest
Flag: com.android.window.flags.show_desktop_experience_dev_option
Change-Id: Ib2eaa99fab1fbcae6ed9afa997cfe92676a75c70