Add test transition to reopen ime window app

Add a new test (only the transition at the moment) that reopens an IME app with focused IME from recents apps and it will check (once we add the assertions) that the IME is still showing.

Test: atest FlickerTests:ReOpenImeWindowTest
Bug: b/171049722
Change-Id: I43f89bb26b6abcaba4b984b0955034bdf41b2977