[llvm] [Support] Introduce formatv variant of createStringError (PR #80493)

[Jakub Kuderski via llvm-commits]

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@@ -1261,6 +1262,15 @@ inline Error createStringError(std::errc EC, char const *Fmt,
   return createStringError(std::make_error_code(EC), Fmt, Vals...);
 }
 
+template <typename... Ts>
+inline Error createStringErrorv(std::error_code EC, const char *Fmt,
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kuhar wrote:

nit: I like the idea but it's really hard for me to tell this apart from the old function -- the only difference is the trailing lowercase `v` at the end. Could we either pick a different name or capitalize it consistently with the function (`V`)? 

https://github.com/llvm/llvm-project/pull/80493