LibURL: Validate for invalid _domain_ code points for non-opaque domains

We were previously not checking for C0 control, U+0025 (%), or U+007F
DELETE.

This makes another good set of URL tests in WPT pass :^)

Tests/LibURL/TestURL.cpp

@@ -512,3 +512,18 @@ TEST_CASE(ascii_only_url)
         EXPECT_EQ(url.to_byte_string(), "http://example.com/iNdEx.HtMl#fRaGmEnT");
     }
 }
+
+TEST_CASE(invalid_domain_code_points)
+{
+    {
+        constexpr auto upper_case_url = "http://example%25.com"sv;
+        URL::URL url(upper_case_url);
+        EXPECT(!url.is_valid());
+    }
+
+    {
+        constexpr auto mixed_case_url = "http://thing\u0007y/'"sv;
+        URL::URL url(mixed_case_url);
+        EXPECT(!url.is_valid());
+    }
+}