[mlir][sparse] implement simple codegen for insertion (and related ops)

This is a proof of concept insertion implementation that sets up
the basic framework and implements it with push backs for just
sparse vectors. It adds insertion/compression through SSA values,
so that we properly update the memref after after pushback operation.

Note that properly using SSA values in sparsification is still TBD
but I will wait until Peiming's loop emitter is in to avoid conflicts.

Reviewed By: wrengr

Differential Revision: https://reviews.llvm.org/D136008