Allow overriding dev option with adb

Use a system property per flag to override whether or not they are in
the developer option. The system property is read when the flag is first
read, the value of the flag is then cached.

Fix: 408432634
Test: atest DesktopExperienceFlagsTest
Flag: com.android.window.flags.show_desktop_experience_dev_option
Change-Id: Idbac67e22e0845c5b2d6d5021f7b2a93890f91fd