Add a flag to enable/disable SupervisionService based on whether the device is...

Add a flag to enable/disable SupervisionService based on whether the device is being managed by the supervision role holder.

Sync mechanism is detailed in go/kf-design-po-no-more.

Change-Id: Ibf1c464bd4ea14d33d97457a6db03cacec6c42ad
Bug: 376213673
Flag: android.app.admin.flags.enable_supervision_service_sync