[IR][Legalization] Split illegal deinterleave and interleave vectors

To make legalization easier, the operands and outputs have the same size for
these ISD Nodes. When legalizing the results in SplitVectorResult the operands
are legalized to the same size as the outputs.
The ISD Node has two output/results, therefore the legalizing functions update
both results/outputs.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D144744