growth: Refactor GrowthInteractor broadcast logic and send to current user.

The broadcast for device entry is now sent using `sendBroadcastAsUser` with `UserHandle.CURRENT`. The delayed broadcast mechanism has been refactored to use `transformLatest` for improved cancellation handling when the device entry state changes.

Bug: 437915291
Flag: com.android.systemui.enable_desktop_growth

Change-Id: Ia5520605ce4a068f8362c3531ea38ab983556d0d