[interop][SwiftToCxx] incorporate argument labels into Stdlib API names in C++

This allows easier use and more wider API exposure from the Swift stdlib

In the future, all functions and method should incorporate argument labels, but it's not yet clear how

test/Interop/SwiftToCxx/stdlib/string/string-in-cxx-execution.cpp

@@ -0,0 +1,43 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %target-swift-frontend -typecheck %t/print-string.swift -typecheck -module-name Stringer -enable-experimental-cxx-interop -emit-clang-header-path %t/Stringer.h
+
+// RUN: %target-interop-build-clangxx -std=gnu++20 -c %t/string-conversions.cpp -I %t -o %t/swift-stdlib-execution.o
+// RUN: %target-build-swift %t/print-string.swift -o %t/swift-stdlib-execution -Xlinker %t/swift-stdlib-execution.o -module-name Stringer -Xfrontend -entry-point-function-name -Xfrontend swiftMain %target-cxx-lib
+// RUN: %target-codesign %t/swift-stdlib-execution
+// RUN: %target-run %t/swift-stdlib-execution | %FileCheck %s
+
+// REQUIRES: executable_test
+
+//--- print-string.swift
+
+@_expose(Cxx)
+public func printString(_ s: String) {
+    print("'''\(s)'''")
+}
+
+//--- string-conversions.cpp
+
+#include <cassert>
+#include "Stringer.h"
+
+int main() {
+  using namespace Swift;
+  using namespace Stringer;
+
+  {
+    auto s = String("Hello world");
+    assert(s.getCount() == 11);
+    printString(s);
+    s.append(String("!test"));
+    printString(s);
+    printString(s.lowercased());
+    printString(s.uppercased());
+  }
+// CHECK: '''Hello world'''
+// CHECK: '''Hello world!test'''
+// CHECK: '''hello world!test'''
+// CHECK: '''HELLO WORLD!TEST'''
+  return 0;
+}