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/ScreenTimeoutSettings.java

@@ -164,7 +164,8 @@ public class ScreenTimeoutSettings extends RadioButtonPickerFragment implements
         final String textMoreDetails = getResources().getString(R.string.admin_more_details);
 
         final SpannableString spannableString = new SpannableString(
-                textDisabledByAdmin + System.lineSeparator() + textMoreDetails);
+                textDisabledByAdmin + System.lineSeparator()
+                + System.lineSeparator() + textMoreDetails);
         final ClickableSpan clickableSpan = new ClickableSpan() {
             @Override
             public void onClick(@NonNull View widget) {
@@ -174,7 +175,7 @@ public class ScreenTimeoutSettings extends RadioButtonPickerFragment implements
 
         if (textDisabledByAdmin != null && textMoreDetails != null) {
             spannableString.setSpan(clickableSpan, textDisabledByAdmin.length() + 1,
-                    textDisabledByAdmin.length() + textMoreDetails.length() + 1,
+                    textDisabledByAdmin.length() + textMoreDetails.length() + 2,
                     Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
         }