Add custom decode structure and enable fusion_tracer
Add custom decode structure and enable fusion_tracer

- Add custom fusion_decode struct with 64-bit immediate
- Change fusion_tracer to extend fusion_emitter
- Fix li state machine logic in fusion_tracer
- Add lui and auipc to fusion_emitter
- Use Imm type for asmjit immediates

rv8-io/rv8,rv8-io/rv8,rv8-io/rv8