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

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

Pushed new version with an update to make Sema::VerifyIntegerConstantExpression slightly more strict.  That handles the cases where the errors were getting dropped.  The tradeoff is that we're more strict about arithmetic overflow in certain integer constant expressions (clang/test/SemaCXX/enum.cpp).

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