[clang] [Clang][Sema] Fix an ICE where structured binding packs within a lambda were not added to the CapturingScopeInfo (PR #214716)

[Yanzuo Liu via cfe-commits]

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zwuis wrote:

This kind of tests should be in `clang/unittests`. AFAIK we don't add such tests if behaviour changes can be observed easily.

https://github.com/llvm/llvm-project/pull/214716