Fix missing IME back animation in widget picker

Discussed with folks who worked on IME animation, and root cause seemed
to be picker unconditionally clearing the focus. Also, there is no
in-built way for clearing focus on other user interactions. So, had to
write custom logic to conditionally clear the focus.

Bug: 369933372
Test: See screencast (tested back, and other user interactions)
Flag: EXEMPT BUGFIX
Change-Id: I693bd27662563e5320159c082eb955a3bd5386f8