[clang-tools-extra] [clang-tidy] Add `bugprone-virtual-arithmetic` check (PR #91951)

[via cfe-commits]

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+.. title:: clang-tidy - bugprone-virtual-arithmetic
+
+bugprone-virtual-arithmetic
+===========================
+
+Warn if pointer arithmetic is performed on a class that declares a
+virtual function.
+
+Pointer arithmetic on polymorphic objects where the pointer's static type is 
+different from its dynamic type is undefined behavior.
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Discookie wrote:

indeed it could happen to any different static and dynamic types, but here it's better to be more specific for clarity, I think. The check only aims to find bugprone polymorphic objects anyways.
(`expr.add` in the standard specifically highlights polymorphic objects as well.)

https://github.com/llvm/llvm-project/pull/91951