[sglang,ci,doc] feat: Update Ascend Dockerfile and docker build workflow to 8.3.RC1 version for VeRL + Sglang

[xiazhahe]

…low to 8.3.RC1 version for VeRL + Sglang

What does this PR do?

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This PR contains following things:
Add new dockerfile with CANN 8.3.RC1 base image, update sglang version
to v0.5.8, sgl-kernel-npu to 46b73de.

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