Add power consumption footer in screen timeout page.

- show this footer when there's no footer about work profile
Screenshots:
[without work profile]: https://screenshot.googleplex.com/5pAD2xBvP6QSBvY
[with work profile]:  https://screenshot.googleplex.com/7BRd6ToAjFN9QZx

Bug: 300245790
Test: manual
Test: make RunSettingsRoboTests ROBOTEST_FILTER="com.android.settings.display.ScreenTimeoutSettingsTest"
Change-Id: I6df018d7758fbec3277179358b17eb11fa1aee34