CANN: Refactor ND to NZ workspace to be per-device (#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.
Co-authored-by: hipudding <huafengchun@gmail.com>
* refactor
Signed-off-by: noemotiovon <757486878@qq.com>
* rename
Signed-off-by: noemotiovon <757486878@qq.com>
* fix review comments
Signed-off-by: noemotiovon <757486878@qq.com>
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Signed-off-by: noemotiovon <757486878@qq.com>
Co-authored-by: hipudding <huafengchun@gmail.com>
