[AMDGPU] Introduce iglp_opt(2): Generalized exp/mfma interleaving for select kernels (llvm#81342)

This implements the basic pipelining structure of exp/mfma interleaving
for better extensibility. While it does have improved extensibility,
there are controls which only enable it for DAGs with certain
characteristics (matching the DAGs it has been designed against).

Author: jrbyrnes