Add trunkstable flags for Fold Lock Setting

Add trunkstable flag for Fold Lock Setting.
FoldLockSettingAvailabilityProvider would check resources and
trunkstable flag and return the availibility of the setting.
Test: Flashed the device with local build
* Locally enabled and disabled the flag
* Check if the behavior and setting visibility is changing according to
  flag status.
Fixes: 302682601
Flag: fold_lock_setting_enabled

Change-Id: Idb7a9519cb2b6ff0116ddf6765e427f9d6733d5e