Enable view anchoring in ActivityStarter.

This change will enable components in SystemUI to register a controller
factory long term, so that all launches and returns from the associated
activity use that factory to generate a controller. See
go/return-animations-framework-design for an idea of what that looks
like (design has evolved since then butthe principle is the same).

Bug: 202516970
Flag: com.android.systemui.shared.return_animation_framework_library
Flag: com.android.systemui.shared.return_animation_framework_long_lived
Test: atest ActivityStarterImplTest LegacyActivityStarterImplTest
Change-Id: I51892424fb196e209c206297d2fc85fa4bf5ac22