[clang] [clang] Introduce "binary" StringLiteral for #embed data (PR #127629)

[via cfe-commits]

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@@ -1752,7 +1752,8 @@ enum class StringLiteralKind {
   UTF8,
   UTF16,
   UTF32,
-  Unevaluated
+  Unevaluated,
+  Binary
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cor3ntin wrote:

Can you add a comment explaining this is for embed?

I'm sorry it took me a while to understand how this patch works.
(The reason is that this allows us to not "cast" to char in `getCodeUnitS()` - which is only used in C23 mode)

Maybe also add a comment in `getCodeUnitS` and/or `CheckC23ConstexprInitStringLiteral`

https://github.com/llvm/llvm-project/pull/127629