Add RayService extra dependency example

[Blaze-DSP]

Description

Add ray-serve.extra-dependency.yaml example demonstrating how to install custom dependencies in RayService containers. The example shows:

• Installing system packages and shared Python dependencies via container args
• Installing application-specific Python dependencies via runtime_env

[JiangJiaWei1103]

Thanks for contributing. Would you mind standardizing the double quoting style? You can refer to #4339 and #4359.

[Blaze-DSP]

Done. Plus the example config has been updated, since there were issues with prv one

[Future-Outlier]

Hi, thanks for the PR!
Using args for dependency installation might be risky.
Since args executes first, if the installation takes > 10 mins, the liveness probe will fail and restart the Pod.
Would postStart be a better approach here?

Suggested change

	# Shared dependencies via args
	# System packages and pip packages installed here are accessible
	# to ALL applications in this RayService
	args:
	- |
	sudo apt-get update && \
	sudo apt-get install -y --no-install-recommends curl && \
	sudo rm -rf /var/lib/apt/lists/* && \
	pip install httpx \
	# Make sure to add the \ at the end of the last line
	# Shared dependencies via lifecycle postStart hook
	# System packages and pip packages installed here are accessible
	# to ALL applications in this RayService
	lifecycle:
	postStart:
	exec:
	command:
	- /bin/bash
	- -c
	- |
	sudo apt-get update && \
	sudo apt-get install -y --no-install-recommends curl && \
	sudo rm -rf /var/lib/apt/lists/* && \
	pip install httpx

[Blaze-DSP]

It is better to do it before ray start, cz if it happens after ray and takes a long time, then the serving will fail incase, dependencies are not present when serve applications starts. I did try with bigger dependencies and it seemed to work for me.

ur thoughts on this?

[Future-Outlier]

I don't think this is a good idea because
when installation > 10 min, kubelet will restart the pod, and we will repeat it again and again

[Future-Outlier]

cc @win5923 @seanlaii to take a look

[Future-Outlier]

cc @rueian to discuss when you have time

[Future-Outlier]

we should build a custom image instead, since this might cause other potential problem like here

cc @rueian

[Future-Outlier]

closes this PR and plz let me know if this is needed for the kuberay project