Add One-handed mode entry point in a11y system controls

Integrate One-handed mode entry in AOSP Settings.
(Settings > A11y > System controls > One-handed mode)

The entry will show if vendor set below system property
  * Property : ro.support_one_handed_mode
Otherwise, the entry will be hidden.

Test: manual check Settings UI
      Settings > A11y > System controls > One-handed mode
Bug: 182144396
Change-Id: I699c576a87057274529ca46dee394c413a4cea2b