[clang-tools-extra] Add check 'modernize-use-enum-class' (PR #138282)

[Baranov Victor via cfe-commits]

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+.. title:: clang-tidy - cppcoreguidelines-use-enum-class
+
+cppcoreguidelines-use-enum-class
+=============================
+
+Finds plain non-class ``enum`` definitions that could use ``enum class``.
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vbvictor wrote:

```suggestion
Finds unscoped (non-class) ``enum`` declarations and suggests using ``enum class`` instead.
```
1. I think we should use original cppreference syntax (unscoped)
2. definitions -> declarations because in tests we also warn on `enum ForwardE`
3. rephrased "could use" because we actually don't check any conditions before giving warning.

https://github.com/llvm/llvm-project/pull/138282