Store the LocationKind of an entry value buffer independently from the main LocationKind (NFC)

This patch hides the logic for setting the location kind of an entry
value inside the begin/finalize/cancel functions. This way we get rid
the strange workaround that is currently in setLocation().

In the future, this will allow us to set the location kind of the
entry value independently from the location kind of the main
expression.

Differential Revision: https://reviews.llvm.org/D96554