Upgrade CANN version to 8.1.rc1 (#747)

### What this PR does / why we need it?

Make CANN version bump separately from
https://github.com/vllm-project/vllm-ascend/pull/708

- Upgrade CANN version to 8.1.rc1
- Add prefix to speed up download
`m.daocloud.io/quay.io/ascend/cann:8.1.rc1-910b-ubuntu22.04-py3.10`
- Address tail sapce for Dockerfile.openEuler
- Add note for `/workspace` and `/vllm-workspace` as followup of
https://github.com/vllm-project/vllm-ascend/pull/741

### Does this PR introduce _any_ user-facing change?
no

### How was this patch tested?

CI passed

Co-authored-by: MengqingCao <cmq0113@163.com>

Signed-off-by: Yikun Jiang <yikunkero@gmail.com>
Co-authored-by: MengqingCao <cmq0113@163.com>

docs/source/quick_start.md

@@ -62,6 +62,8 @@ docker run --rm \
 ::::
 :::::
 
+The default workdir is `/workspace`, vLLM and vLLM Ascend code are placed in `/vllm-workspace` and installed in [development mode](https://setuptools.pypa.io/en/latest/userguide/development_mode.html)(`pip install -e`) to help developer immediately take place changes without requiring a new installation.
+
 ## Usage
 
 You can use Modelscope mirror to speed up download: