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

[Vikram Hegde via cfe-commits]

vikramRH wrote:

@yuanfang-chen , @AaronBallman, @shafik,  are we still actively looking into this ? (I would be willing to commandeer this if its not high on your priority list)

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