fix: Clang 19 -Wc++20-extensions warning in template test macros (cat…

…chorg#2910)

- Added INTERNAL_CATCH_TEMPLATE_TEST_CASE_HANDLE_EMPTY macro for Clang 19+
- Modified template test case macro expansion path for Clang 19+
- Keeps original behavior for other compilers and older Clang versions

src/catch2/catch_template_test_macros.hpp

@@ -1,4 +1,3 @@
-
 //              Copyright Catch2 Authors
 // Distributed under the Boost Software License, Version 1.0.
 //   (See accompanying file LICENSE.txt or copy at
@@ -8,15 +7,10 @@
 #ifndef CATCH_TEMPLATE_TEST_MACROS_HPP_INCLUDED
 #define CATCH_TEMPLATE_TEST_MACROS_HPP_INCLUDED
 
-// We need this suppression to leak, because it took until GCC 10
-// for the front end to handle local suppression via _Pragma properly
-// inside templates (so `TEMPLATE_TEST_CASE` and co).
-// **THIS IS DIFFERENT FOR STANDARD TESTS, WHERE GCC 9 IS SUFFICIENT**
 #if defined(__GNUC__) && !defined(__clang__) && !defined(__ICC) && __GNUC__ < 10
 #pragma GCC diagnostic ignored "-Wparentheses"
 #endif
 
-
 #include <catch2/catch_test_macros.hpp>
 #include <catch2/internal/catch_template_test_registry.hpp>
 #include <catch2/internal/catch_preprocessor.hpp>