[clang] [HLSL] Convert vectors to bool for unary ! (PR #163857)

[Chris B via cfe-commits]

llvm-beanz wrote:

@erichkeane might be the right person to weigh in on the C/C++ side, but my guess is that C++ does what it currently does intentionally for compatibility with SSE where boolean true in vectors is expected to be all bits on (so sign-extending i1 gets the intended result).

https://github.com/llvm/llvm-project/pull/163857