Introduce Window.setContentOnApplyWindowInsetsListener

When root-level content containers fit insets, they used to just
apply and consume the entire system insets. However, with the new
Inset APIs, and with deprecating ADJUST_RESIZE IME flag, we want
to give apps an easy way to customize this behavior.

For that, we introduce Window.setOnContentApplyWindowInsetsListener
that returns what kind of margins/padding should be applied and
what should be dispatched to the content views. This is essentially
a replacement for SYSTEM_UI_FLAG_LAYOUT_* as well as
SOFT_INPUT_ADJUST_RESIZE: It allows apps to choose which insets
should be handled on the window level vs view level.

For that, we mark the window decor views as
FRAMEWORK_OPTIONAL_FIT_SYSTEM_WINDOWS, in order to distinguish the
case when support library calls makeOptionalFitSystemWindows(). This
is because of two reasons:
- We don't want the listener to be invoked twice.
- We can not do the compat ping-pong between onApplyWindowInsets
and fitSystemWindows. This is because during the ping-pong, the
result of the OnContentApplyWindowInsetsListener would be lost.
However, we still need to do the compat ping-pong for
ActionBarOverlayLayout in the support library (until that gets
migrated to use onApplyWindowInsets), so we have this separate
dispatching path that only gets used for framework optional
fitting views.

Test: WindowTest
Bug: 118118435
Change-Id: I4b514addd9e094163062d651972f85615b4a35db