[objc-arc] Convert the bodies of ARCInstKind predicates into covered switches.

[objc-arc] Convert the bodies of ARCInstKind predicates into covered switches.

This is much better than the previous manner of just using
short-curcuiting booleans from:

1. A "naive" efficiency perspective: we do not have to rely on the
compiler to change the short circuiting boolean operations into a
switch.
2. An understanding perspective by making the implicit behavior of
negative predicates explicit.
3. A maintainability perspective through the covered switch flag making
it easy to know where to update code when adding new ARCInstKinds.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229906 91177308-0d34-0410-b5e6-96231b3b80d8