[clang] [ExprConstant] Handle shift overflow the same way as other kinds of overflow (PR #99579)

[Shafik Yaghmour via cfe-commits]

https://github.com/shafik commented:

Thank you for the additional tests, so I am not sure if the coverage is sufficient I see changed under the following diagnostic:

note_constexpr_negative_shift
note_constexpr_large_shift
note_constexpr_lshift_of_negative
note_constexpr_lshift_discards

but I don't think I see tests that cover the negative shift changes, am I just missing it?

https://github.com/llvm/llvm-project/pull/99579