Improve char printing (#167899)

This PR outputs chars to stream without building temporary strings.
They were modified by (on fish)
```
sed  -i -e 's/<< "\([^\\\']\)"/<< \'\1\'/g' (grep '<< "."' -r torch c10 aten -l)
```
and revert some invalid changes.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/167899
Approved by: https://github.com/Skylion007

c10/test/core/DispatchKeySet_test.cpp

@@ -435,7 +435,7 @@ TEST(DispatchKeySet, TestFunctionalityDispatchKeyToString) {
     if (i > 0) {
       ASSERT_TRUE(res.find("Unknown") == std::string::npos)
           << i << " (before is " << toString(static_cast<DispatchKey>(i - 1))
-          << ")";
+          << ')';
     } else {
       ASSERT_TRUE(res.find("Unknown") == std::string::npos) << i;
     }

c10/test/util/Half_test.cpp

@@ -96,10 +96,10 @@ TEST(HalfConversionTest, TestPorableConversion) {
   for (auto x : inputs) {
     auto target = c10::detail::fp16_ieee_to_fp32_value(x);
     EXPECT_EQ(halfbits2float(x), target)
-        << "Test failed for uint16 to float " << x << "\n";
+        << "Test failed for uint16 to float " << x << '\n';
     EXPECT_EQ(
         float2halfbits(target), c10::detail::fp16_ieee_from_fp32_value(target))
-        << "Test failed for float to uint16" << target << "\n";
+        << "Test failed for float to uint16" << target << '\n';
   }
 }
 

c10/test/util/logging_test.cpp

@@ -98,7 +98,7 @@ struct Noncopyable {
 };
 
 std::ostream& operator<<(std::ostream& out, const Noncopyable& nc) {
-  out << "Noncopyable(" << nc.x << ")";
+  out << "Noncopyable(" << nc.x << ')';
   return out;
 }
 } // namespace