[clang-tools-extra] [clang-tidy] Teach `readability-uppercase-literal-suffix` about C++23 and C23 suffixes (PR #148275)

[Baranov Victor via cfe-commits]

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@@ -225,6 +226,89 @@ void integer_complex_suffix() {
   static_assert(v28 == 1J, "");
 }
 
+// This is a C++23 feature, but Clang supports it in earlier language modes
+// as an extension, so we test it unconditionally.
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vbvictor wrote:

I think we should not depend on clang extension and strictly follow C++ standard. This could mitigate unexpected problems in the future. I'd ask to place it in c++23 tests.
Maybe other reviewers have different opinion on this matter, WDYT reviewers?

https://github.com/llvm/llvm-project/pull/148275