[ASTDumper] Respect function body skipping

Avoid parsing a body for e.g
`-experimental-skip-all-function-bodies`.

lib/AST/ASTDumper.cpp

@@ -1561,7 +1561,8 @@ namespace {
         });
       }
 
-      if (auto Body = D->getBody(/*canSynthesize=*/ParseIfNeeded)) {
+      auto canParse = ParseIfNeeded && !D->isBodySkipped();
+      if (auto Body = D->getBody(canParse)) {
         printRec(Body, &D->getASTContext());
       }
     }

test/Frontend/dump-parse-skip-function-body.swift

@@ -0,0 +1,6 @@
+// RUN: %target-swift-frontend -dump-parse -experimental-skip-all-function-bodies %s | %FileCheck %s
+
+func foo() {
+  print("hello")
+}
+// CHECK-NOT: brace_stmt