Replace dynamic summary text for SettingPref

All SettingPrefs that have dynamic summaries are replaced
by placeholder text. Changes are for:
- Battery Saver "Turn on automatically"
- Notification "Dock speaker plays"
- Notification "Emergency tone"

Bug: 36101902
Test: make RunSettingsRoboTests
Change-Id: Ic2556055c155989015dbef6b507d3e3b45b779b5