[clang] [Clang] Implement diagnostics for why `std::is_standard_layout` is false (PR #144161)

[Corentin Jabot via cfe-commits]

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@@ -1787,6 +1788,13 @@ def note_unsatisfied_trait_reason
            "%NonReplaceableField{has a non-replaceable member %1 of type %2}|"
            "%NTCBase{has a non-trivially-copyable base %1}|"
            "%NTCField{has a non-trivially-copyable member %1 of type %2}|"
+           "%NonStdLayoutBase{has a non-standard-layout base %1}|"
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cor3ntin wrote:

```suggestion
           "%NonStandardLayoutBase{has a non-standard-layout base %1}|"
```
(std is a confusing abbreviation in the context of C++)

https://github.com/llvm/llvm-project/pull/144161