[sparse][mlir] simplify lattice optimization logic

Simplifies the way lattices are optimized with less, but more
powerful rules. This also fixes an inaccuracy where too many
lattices resulted (expecting a non-existing universal index).
Also puts no-side-effects on all proper getters and unifies
bufferization flags order in integration tests (for future,
more complex use cases).

Reviewed By: bixia

Differential Revision: https://reviews.llvm.org/D97134