Revert: [XLA:GPU] Store fusion_roots and fusion_heroes as HloInstructionAdaptor in HloFusionAnalysis.
Revert: [XLA:GPU] Store fusion_roots and fusion_heroes as HloInstructionAdaptor in HloFusionAnalysis.

Internal tests are failing.

Reverts 73a3f15becb844358808b7c6686b15fe5d0baecf
