Create PresentationController

This change is a pure refactoring (mostly just moving the code
added in [1] into PresentationController(Tests)).
PresentationController manages all the presentation windows and
applies relevant policies to them.

Given that we'll put adding/removing presentations into a
transition and that we'll add more policies to presentations,
PresentationController helps encapsulate and better maintain all
such logic in one place.

[1] I26108aa0bc0cac320c8fb50ea67543981ab77e23

Flag: com.android.window.flags.enable_presentation_for_connected_displays
Bug: 394507839
Test: WmTests:PresentationControllerTests
Change-Id: I0b658ce52c81cb58916f08ee552e7e77683e42c5