[ADT] Deprecate a soft-deprecated APInt constructor (#166314)

This patch deprecates an APInt constructor that has been
soft-deprecated via comments since:

  commit 7a16288157efc5fb85fbe3b8b4c37071da7609a6
  Author: Jeffrey Yasskin <jyasskin@google.com>
  Date:   Mon Jul 18 21:45:40 2011 +0000

This patch updates a small number of remaining uses.

GitOrigin-RevId: ed7d6c3511df7f5d1dbf52579740f7f4e4ada4f9