[CI/Build] bump Dockerfile.neuron image base, use public ECR

[dtrifiro]

The current Neuron base image fails to build in CI due to a malformed requirements string.

It also seems that the current image is not public. I switched over to the image provided in https://github.com/aws-neuron/deep-learning-containers?tab=readme-ov-file#pytorch-inference-neuronx

[github-actions]

👋 Hi! Thank you for contributing to the vLLM project.
Just a reminder: PRs would not trigger full CI run by default. Instead, it would only run fastcheck CI which consists a small and essential subset of CI tests to quickly catch errors. You can run other CI tests on top of default ones by unblocking the steps in your fast-check build on Buildkite UI.

Once the PR is approved and ready to go, please make sure to run full CI as it is required to merge (or just use auto-merge).

To run full CI, you can do one of these:

• Comment /ready on the PR
• Add ready label to the PR
• Enable auto-merge.

🚀

[njhill]

@liangfu does this look ok to you?

[WoosukKwon]

@liangfu Could you please take a look?

[dtrifiro]

@liangfu any chance this could get merged?

[dtrifiro]

@njhill @WoosukKwon since CI is passing and the build does not actually work for neuron, how about merging this? This would also unblock #4738

[liangfu]

the changes looks good. thanks for the contribution, and sorry for the late reply.