Fix sentence capitalization of locale names.

It turns out that out previous CL [1] is not sufficient to address all
the requests regarding capitalization.

With [1], now InputMethodSubtype#getLocaleDisplayName() returns a locale
name whose capitalization is basically optimized to be used as a list
item.  It works well for list UI, but on a UI element that looks like a
sentence text, we still need to capitalize the first character.

This CL takes care of those UI elements in the Settings app.  This CL
also addresses a remaining TODO about locale-unaware text formatting by
using about android.icu.text.ListFormatter.

  [1]: If105082ce703db7a86738455db7e9fb37f3c6fe8
       e489baf96df2837a3a63b626d9023a4a8b322c28

Bug: 29035638
Change-Id: I59f93f0bc067cdd87c6065c972a7da3cde1128f9