Follow footer preference guildance on some pages

- Footer preference should have a info icon in tethering page.
- Rmove an empty icon for screen attention setting.
- Revise the "More details" to "Learn more"
- Add more empty line between footer info and "Learn more"

Test: Built apk, and check the screen
Fix: 183472971
Fix: 183472858
Change-Id: I7edb71639b59efb8205c0ef6a50ab483f88aa63d

src/com/android/settings/display/AdaptiveSleepPreferenceController.java

@@ -60,7 +60,6 @@ public class AdaptiveSleepPreferenceController {
         mPreference = new RestrictedSwitchPreference(context);
         mPreference.setTitle(R.string.adaptive_sleep_title);
         mPreference.setSummary(R.string.adaptive_sleep_description);
-        mPreference.setIcon(R.drawable.empty_icon);
         mPreference.setChecked(isChecked());
         mPreference.setKey(PREFERENCE_KEY);
         mPreference.setOnPreferenceClickListener(preference -> {