[CodeGen] Improve speed of ComplexDeinterleaving pass

Cache all results of running `identifyNode`, even those that do not identify
potential complex operations. This patch prevents ComplexDeinterleaving pass
from repeatedly trying to identify Nodes for the same pair of instructions.

Fixes https://github.com/llvm/llvm-project/issues/64379

Differential Revision: https://reviews.llvm.org/D156916