[clang] [clang] Limit alignment for emitted vectors (PR #98629)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

> max aligment [...] LLVM Verifier accepts is 2^14

The verifier limit in most places is 2^32.  It looks like 2^14 is specifically for ByVal.  And there isn't really any good reason for that limit; it was arbitrarily chosen in b567e3ffb0, nearly two decades ago, and could easily be changed if we want.

Can we just fix the backend so ByVal has the same alignment limit as everything else?  I really don't want the complexity of multiple different alignment limits here.

https://github.com/llvm/llvm-project/pull/98629