CANN: add RoPE cache preload before ACL graph capture (llama/20747)

CANN: add RoPE cache preload before ACL graph capture (llama/20747)

ACL graph capture disallows host-to-device memcpy and device memory
malloc/free on the captured stream. Pre-load the RoPE cache before
capture so that:
- Host-to-device copies and allocations run on the non-captured stream
- Cache metadata is populated and memory pool is warmed up
- During capture, only on-device computations are recorded; host-side
  and allocation branches are skipped