Show accessibility floating menu after user unlock their phone

* Accessibiltiy floating menu needs to retrieve information from AccessibilityManagerService and it will be ready before receiving onUserUnlocked()
* When enter the lockscreen, destroy the accessibility floating menu; when exist the lockscreen, show the accessibility floating menu.

Bug: 184272107
Bug: 178285746
Test: atest AccessibilityFloatingMenuControllerTest
Change-Id: I052a57296fab2afa243bd6b696bdfdb4235599a3