Update battery settings strings

1. Change "screenTime" to "lastFullChargeTime" in high usage dialog
2. Update "Background restriction" strings
3. Update footer string

Bug: 73018395
Test: RunSettingsRoboTests
Change-Id: I07c149123c4ee1a69dd81c9a9e6eaa5df69b60b4

src/com/android/settings/fuelgauge/batterytip/BatteryTipDialogFragment.java

@@ -102,7 +102,10 @@ public class BatteryTipDialogFragment extends InstrumentedDialogFragment impleme
 
                 return new AlertDialog.Builder(context)
                         .setMessage(getString(R.string.battery_tip_dialog_message,
-                                highUsageTip.getHighUsageAppList().size()))
+                                highUsageTip.getHighUsageAppList().size(),
+                                StringUtil.formatRelativeTime(context,
+                                        highUsageTip.getLastFullChargeTimeMs(),
+                                        false /* withSeconds */)))
                         .setView(view)
                         .setPositiveButton(android.R.string.ok, null)
                         .create();