[libc++] Apply clang formatting to all string unit tests

This applies clang-format to the std::string unit tests in preparation
for landing https://reviews.llvm.org/D140550.

Differential Revision: https://reviews.llvm.org/D140612

libcxx/test/std/strings/basic.string/string.ops/string_compare/string.pass.cpp

@@ -16,21 +16,18 @@
 #include "test_macros.h"
 #include "min_allocator.h"
 
-TEST_CONSTEXPR_CXX20 int sign(int x)
-{
-    if (x == 0)
-        return 0;
-    if (x < 0)
-        return -1;
-    return 1;
+TEST_CONSTEXPR_CXX20 int sign(int x) {
+  if (x == 0)
+    return 0;
+  if (x < 0)
+    return -1;
+  return 1;
 }
 
 template <class S>
-TEST_CONSTEXPR_CXX20 void
-test(const S& s, const S& str, int x)
-{
-    LIBCPP_ASSERT_NOEXCEPT(s.compare(str));
-    assert(sign(s.compare(str)) == sign(x));
+TEST_CONSTEXPR_CXX20 void test(const S& s, const S& str, int x) {
+  LIBCPP_ASSERT_NOEXCEPT(s.compare(str));
+  assert(sign(s.compare(str)) == sign(x));
 }
 
 TEST_CONSTEXPR_CXX20 bool test() {
@@ -85,8 +82,7 @@ TEST_CONSTEXPR_CXX20 bool test() {
   return true;
 }
 
-int main(int, char**)
-{
+int main(int, char**) {
   test();
 #if TEST_STD_VER > 17
   static_assert(test());