[clang] [clang][ExprConst] allow single element access of vector object to be constant expression (PR #72607)

[Vikram Hegde via cfe-commits]

vikramRH wrote:

> Hello @vikramRH, please feel free to commandeer this.

Thanks @yuanfang-chen. Also, clang already rejects expressions like &V[0] (https://godbolt.org/z/eGcxzGo66), which is also true with constexprs and this PR. What's the specific concern here ?

https://github.com/llvm/llvm-project/pull/72607