Several improvements and bug fixes to the inline autofill flow

* Pipe the augmented autofill's inline actions through to the
  InlineSuggestionsResponse
* Do not send the inline action if the number of inline suggestions is
  zero
* Refactor autofill inline suggstion session so that all the calls to
  the IME has happens within the class
* Send an empty response to IME to hide the inline suggestion UI  when
  view exits and the previous response wasn't empty

Test: manual verification, atest InlineLoginActivityTest
Bug: 149522488
Bug: 150312201

Change-Id: I7a0dbf44e9fad6e7da857448c0f2b186e1681d17