settings: add accessibility events to lockscreen slider and shortcuts (2/2)

beside that it is nicer for ppl using talkback eg and get clear
instructions this solves as well a fc in settings lockscreen targets
when using accessibility services

fix wrong value assignment to settings provider on longpress option for
lockscreen shortcuts

Change-Id: I4fbda8017b65178c1e29d6b7c24a85ac5a0d3306