Reduce duplication between quickstart user guides

[liu-cong]

There are quite some duplicated content between user guides (e.g., prerequisites, test model endpoint with inference requests). We should extract shared content into a common place, and restructure each user guide to something like below:

## Overview

## Prerequisites
### [Refer to shared] Common Prerequisites (e.g., create HF token, install gateway control plane, install CRDs, etc.)
## Additional

## Installation steps
###[Refer to shared] Common installation
## Additional

## Verification
### [Refer to shared] Common Verification 
## Additional

## Cleanup
### [Refer to shared] Common Cleanup
## Additional

[github-actions]

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[liu-cong]

We should address this with overall modular installation architecture effort