[63/n] Create LetterboxDependenciesHelper to handle different form factors

Other form factors (e.g. Auto) have different Dagger dependencies and
they need to understand if Desktop Windowing is available.

LetterboxDependenciesHelper allows to encapsulate all the configurations
related to the availability of other features on different form factors.
For instance, on Auto, Desktop Windowing is not available and we should
then treat the related transactions differently.

Flag: EXEMPT refactoring
Bug: 423915680
Test: atest WMShellUnitTests:DefaultLetterboxDependenciesHelperTest

Change-Id: I553990b37994374b24db93c2522927c39e83ee51