[mlir][Vector] Add support for 0-D vectors to vector.insert/extract

This is part of the process to remove vector.insertelement/extractelement
from the Vector dialect.

RFC: https://discourse.llvm.org/t/rfc-psa-remove-vector-extractelement-and-vector-insertelement-ops-in-favor-of-vector-extract-and-vector-insert-ops

Differential Revision: https://reviews.llvm.org/D152644