feat: make epp-standalone be its own chart

[capri-xiyue]

What type of PR is this?

/kind feature
What this PR does / why we need it:
Enable users to install epp-standalone mode via helm chart
I made inference-extension be a library chart
Bothepp-standalone and inferencepool will call inference-extension library chart.

In short,

• moved all epp-related resources into config/charts/inference-extension
• config/charts/epp-standalone be a application chart used to deploy epp-standalone mode
• config/charts/inferencepool with user face not changed.
• refactorconfig/charts/inferencepool/templates/rbac.yaml to be config/charts/inferencepool/templates/rbac.yaml and config/charts/epp-standalone/templates/epp-rbac.yaml as some rbac is for inferencepool and some rbac is for epp
• refactorconfig/charts/inferencepool/templates/gke.yaml to be config/charts/inferencepool/templates/rbac.yaml and config/charts/epp-standalone/templates/epp-gke.yaml as some gke set up is for inferencepool and some rbac is for epp

See #2063
Which issue(s) this PR fixes:

Fixes #2063

Does this PR introduce a user-facing change?:
Users can install epp standalone via

helm install vllm-llama3-8b-instruct-standalone ./config/charts/epp-standalone \
  --set inferenceExtension.endpointsServer.endpointSelector="app=vllm-llama3-8b-instruct" \
  --set provider.name=gke 

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[capri-xiyue]

assign @ahg-g

[capri-xiyue]

/retest

[ahg-g]

This is an amazing refactor!

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahg-g, capri-xiyue

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[nirrozenbaum]

@capri-xiyue out of curiosity, do we need all these template files, each with a single line of include statement?
or could it be implemented in a single template file, e.g., inference-extension.yaml where it's content would be all the include statements with a separator?
e.g., something like:

{{- include "inference-extension.config" . -}}
---
{{- include "inference-extension.deployment" . -}}
---
{{- include "inference-extension.gke" . -}}
...
...

[capri-xiyue]

@capri-xiyue out of curiosity, do we need all these template files, each with a single line of include statement? or could it be implemented in a single template file, e.g., inference-extension.yaml where it's content would be all the include statements with a separator? e.g., something like:

{{- include "inference-extension.config" . -}}
---
{{- include "inference-extension.deployment" . -}}
---
{{- include "inference-extension.gke" . -}}
...
...

@nirrozenbaum I will try how one yaml include works for me or not.