[Docs] Add NPU support page and add set device.

[luomaoling]

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Motivation

Add NPU result.

Modification

Add docs/en/device/npu.md, add docs/zh_CN/device/npu.md, add set device.

BC-breaking (Optional)

Does the modification introduce changes that break the backward-compatibility of the downstream repos?
None.

Use cases (Optional)

None.

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDet or MMDet3D.
4. The documentation has been modified accordingly, like docstring or example tutorials.