tint: Reduce repetition for ty.type_name()

Rename the type_name() method with  operator().

`ty.type_name("blah")` becomes `ty("blah")`

Change-Id: Ia0b2bc304e7bb208c2e40a469332044b394535d9
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/118401
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Kokoro: Ben Clayton <bclayton@chromium.org>
Reviewed-by: James Price <jrprice@google.com>
Commit-Queue: Ben Clayton <bclayton@chromium.org>
diff --git a/src/tint/resolver/resolver_test_helper.h b/src/tint/resolver/resolver_test_helper.h
index 647e3ee..d5a6698 100644
--- a/src/tint/resolver/resolver_test_helper.h
+++ b/src/tint/resolver/resolver_test_helper.h
@@ -565,7 +565,7 @@
             auto* type = DataType<T>::AST(b);
             b.AST().AddTypeDecl(b.ty.alias(name, type));
         }
-        return b.ty.type_name(name);
+        return b.ty(name);
     }
     /// @param b the ProgramBuilder
     /// @return the semantic aliased type