[move-only] Add helper method SILType::isMoveOnlyType().

This allows one to know that the type is for a first class move only type and
not a move only wrapped type.

Previously, I did this by checking type.isMoveOnly() &&
!type.isMoveOnlyWrapped(). Better to just have a helper that semantically does
this rather than using a code pattern that doesn't semantically say what it
actually does unless one knows the intent.

Author: gottesmm

include/swift/SIL/SILType.h

@@ -622,6 +622,10 @@ class SILType {
   /// wrapped type.
   bool isMoveOnly() const;
 
+  /// Returns true if and only if this type is a first class move only
+  /// type. NOTE: Returns false if the type is a move only wrapped type.
+  bool isMoveOnlyType() const;
+
   /// Returns true if this SILType is a move only wrapper type.
   ///
   /// Canonical way to check if a SILType is move only. Using is/getAs/castTo

lib/SIL/IR/SILType.cpp

@@ -935,10 +935,16 @@ SILType::getSingletonAggregateFieldType(SILModule &M,
   return SILType();
 }
 
-// TODO: Create isPureMoveOnly.
 bool SILType::isMoveOnly() const {
   if (auto *nom = getNominalOrBoundGenericNominal())
     if (nom->isMoveOnly())
       return true;
   return isMoveOnlyWrapped();
 }
+
+bool SILType::isMoveOnlyType() const {
+  if (auto *nom = getNominalOrBoundGenericNominal())
+    if (nom->isMoveOnly())
+      return true;
+  return false;
+}