[clang] [clang][Sema] Reject negative tuple sizes (PR #159579)

[Shafik Yaghmour via cfe-commits]

https://github.com/shafik commented:

You mention `UnsignedOrNone` in the summary but that is not directly involved in the code you modify. It looks like it is used in `GetDecompositionElementCount` which uses `isTupleLike` but the connection is not obvious.

https://github.com/llvm/llvm-project/pull/159579