Add a broadcast to manifest-register receivers for power save mode changes.

The android.os.action.POWER_SAVE_MODE_CHANGED broadcast already exists for context-registered receivers, this additionally sends the broadcast to a manifest-registered receiver specified in config_powerSaveModeChangedListenerPackage string.

Bug: 149978380
Test: manual using demo apk
Change-Id: I6a363650da7aee11f8f820a0ff78e7a2ec434fad