[mlir][vector] Support vector.extractelement distribution of 1D vectors

Ops such as `%1 = vector.extractelement %0[%pos : index] : vector<96xf32>`.

In case of an extract from a 1D vector, the source vector is distributed. The lane into which the requested position falls, extracts the element and shuffles it to all other lanes.

Differential Revision: https://reviews.llvm.org/D137336