Introduce ComposableControllerFactory.

This Compose-specific controller factory will be used to ensure that
composables are available as soon as composed and only while composed.

Bug: 202516970
Flag: EXEMPT unused, will be protected on usage
Test: manual with prototype, see ag/31506293
Change-Id: I33491b6d50c075ccca19e4ffe1b1ca83049447c3