[clang] [CIR] Upstream Vector support in elementTypeIfVector (PR #140125)

[Andy Kaylor via cfe-commits]

https://github.com/andykaylor approved this pull request.

In case it wasn't clear from my comment on the binop lowering PR, I was suggesting that the unary op and bin op PRs could be combined, but I said that before I saw this one. Since you've already done this, let's just keep them separate.

https://github.com/llvm/llvm-project/pull/140125