[llvm] [ADT] Introduce a `static_cast_to` (PR #165803)

[Jakub Kuderski via llvm-commits]

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@@ -1704,6 +1704,11 @@ auto sum_of(R &&Range, E Init = E{0}) {
   return accumulate(std::forward<R>(Range), std::move(Init));
 }
 
+/// Return a range where each value of `R` is static_cast to `T`
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kuhar wrote:

```suggestion
/// Returns a range where each value of `R` is static_cast to `T`
```

https://github.com/llvm/llvm-project/pull/165803