feat(platform/a2a3): Add register-based task dispatch for host_build_…

[ChaoZheng109]

…graph runtime

Implement register-based communication between AICPU and AICore for a2a3 platform with host_build_graph runtime, using hardware SPR access for task dispatch and status polling.

Architecture:

• Platform layer (a2a3): Register access primitives and address retrieval
• Runtime layer (host_build_graph): Task dispatch and status polling logic

Platform changes (a2a3):

• Add AICore register read/write APIs (aicpu_regs.h/cpp, host_regs.h/cpp)
• Implement register address retrieval via CANN HAL (get_aicore_regs)
• Add register configuration constants in platform_config.h
• Support physical_core_id tracking for register mapping

Runtime changes (host_build_graph):

• Replace memory-based handshake with register-based dispatch
• Use DATA_MAIN_BASE register for task_id dispatch (encoding: task_id+1)
• Use COND register for status polling (IDLE=0, BUSY=1)
• Add Runtime.regs field for register address array
• Track executing_task_ids[] in AICPU executor