[AMDGPU] Allow for MFMA Inst Clustering

This patch adds cluster edges between independent MFMA instructions. Additionally, it propogates all predecessors of cluster insts to the root of the cluster(s), and all successors to the leaf(ves) of the cluster(s) -- this is done to remove the possibility that those insts will be interspersed within the cluster.

Reviewed By: kerbowa

Differential Revision: https://reviews.llvm.org/D124678