[analyzer] NFC: Track all constructed objects in a single state trait.

ExprEngine already maintains three internal program state traits to track
path-sensitive information related to object construction: pointer returned by
operator new, and pointer to temporary object for two different purposes - for
destruction and for lifetime extension. We'll need to add 2-3 more in a few
follow-up commits.

Merge these traits into one because they all essentially serve one purpose and
work similarly.

Differential Revision: https://reviews.llvm.org/D47303

llvm-svn: 333719