Moving media host dependency to composables package

Since MediaHost is considered a view class. It should not be a
dependency of a view-model. It should be known to view classes which is
ShadeScene in this case. This CL moves the setting up code of MediaHost
to a view class.

Bug: 296122467
Test: atest SystemUITests
Test: manual
Flag: ACONFIG com.android.systemui.media_in_scene_container DEVELOPMENT
Change-Id: I2770cd5092a03e6332f8ac8e78ea0eef331f11af