CANN: Refactor ND to NZ workspace to be per-device (llama/15763)
* CANN:Refactor ND to NZ workspace to be per-device in Ascend backend
- Replaced the previous single global ND→NZ workspace with a per-device
cache using unordered_map keyed by device ID.
- Functions `release_nz_workspace`, `relloc_nz_workspace`, and
`get_nz_workspace` now manage workspace independently for each device,
preventing memory conflicts in multi-device / pipeline parallel scenarios.
- This change fixes potential precision issues caused by workspace
overwrites when multiple devices perform ND→NZ conversions concurrently.
overview / pkg / ggml / sources / ggml / commit