Rename ACONFIG flag and add flag wrapper

Rename enable_keyguard_compose to compose_lockscreen.
Also add a flag wrapper which enables flag dependencies.

Test: Ensure that code compiles. Try different flag combinations.
Bug: 301968149
Flag: ACONFIG com.android.systemui.compose_lockscreen DEVELOPMENT

Change-Id: I18aeb62f5e16bd4b656179fe91e8e370c1d1232d