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
diff --git a/packages/SystemUI/aconfig/systemui.aconfig b/packages/SystemUI/aconfig/systemui.aconfig
index 3db99f28..0b24442 100644
--- a/packages/SystemUI/aconfig/systemui.aconfig
+++ b/packages/SystemUI/aconfig/systemui.aconfig
@@ -365,9 +365,9 @@
 }
 
 flag {
-   name: "enable_keyguard_compose"
+   name: "compose_lockscreen"
    namespace: "systemui"
-   description: "Enables the compose version of keyguard."
+   description: "Enables the compose version of lockscreen that runs standalone, outside of Flexiglass."
    bug: "301968149"
 }