[NFC] TypeLowering: Extracted one field verify.

Moved verification of lexical field into its own function in preparation
for verifying a second field.

Author: nate-chandler

include/swift/SIL/TypeLowering.h

@@ -1282,6 +1282,9 @@ class TypeConverter {
   void verifyLowering(const TypeLowering &, AbstractionPattern origType,
                       CanType origSubstType,
                       TypeExpansionContext forExpansion);
+  void verifyLexicalLowering(const TypeLowering &, AbstractionPattern origType,
+                             CanType origSubstType,
+                             TypeExpansionContext forExpansion);
   bool visitAggregateLeaves(
       Lowering::AbstractionPattern origType, CanType substType,
       TypeExpansionContext context,

lib/SIL/IR/TypeLowering.cpp

@@ -2941,6 +2941,13 @@ void TypeConverter::verifyLowering(const TypeLowering &lowering,
                                    AbstractionPattern origType,
                                    CanType substType,
                                    TypeExpansionContext forExpansion) {
+  verifyLexicalLowering(lowering, origType, substType, forExpansion);
+}
+
+void TypeConverter::verifyLexicalLowering(const TypeLowering &lowering,
+                                          AbstractionPattern origType,
+                                          CanType substType,
+                                          TypeExpansionContext forExpansion) {
   // Non-trivial lowerings should always be lexical unless all non-trivial
   // fields are eager move.
   if (!lowering.isTrivial() && !lowering.isLexical()) {