[llvm] [DAGCombiner] Handle extending EXTRACT_VECTOR_ELTs in calculateByteProvider (PR #83963)

[Luke Lau via llvm-commits]

lukel97 wrote:

For reference, this was the failing assertion that I believe needs to be adjusted to handle the vector case:

https://github.com/llvm/llvm-project/blob/0c4736338596d6e527e286b7b551af4bb8b63a55/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp#L8555-L8560

https://github.com/llvm/llvm-project/pull/83963