[clang] [clang][X86] Allow VALIGND/Q element-shift intrinsics in constexpr evaluation (PR #168206)

[Muhammad Abdul via cfe-commits]

0xzre wrote:

> Tests should be added to the existing avx512*builtins.cpp files next to the corresponding intrinsics test coverage using the TEST_CONSTEXPR helpers - see #164078 for an example

Implemented the tests 👍

https://github.com/llvm/llvm-project/pull/168206