Do not click on TVs in PipKeyboardTest

Implement an alternative way of showing/hiding IME in PipKeyboardTest on
TV - via "re-launching" the ImeActivity with a particular action. The
original way - calling UiObject2.click() on the EditText does not work
well on TVs, because the touch events injected by the Instrumentation to
emulate the click force TV into the touch mode.

Bug: 176413558
Test: atest WMShellFlickerTests:PipKeyboardTest
Change-Id: Id3462eba548c8ed639ba44437db573928348c1e6