[clang] [Clang][AArch64] Allow FP8 Neon vector types to be used by __builtin_shufflevector (PR #119031)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

My concern here is there's a tradeoff: there's less complexity constructing the type, maybe, but as a result you've scattered checks all over the code for a type that's basically the same as a VectorType.  At first glance, this doesn't seem like the right tradeoff.

https://github.com/llvm/llvm-project/pull/119031