Make accessibility services able to enable/disable a specified
IME in the same package for the current user.
Bug: 195476910
Fix: 191386474
Test: atest AccessibilitySoftKeyboardTest. Also tested with
modified talkback (use the swith input method API for enable
ime), and self created empty a11y service with an empty ime.
Mananged device and profile which set limit on user 0 are also
tested.
Change-Id: I4187468076705ac597d680f2f5dc32d7b166da1f
b5f3d34def