feat: XCHG-15232 update publish app guide with the new Exchange flow

[zinap-ensemble]

Description

I am a developer on the Adobe Exchange team. We recently updated the App Builder workflows and design, so I created this PR to align the public documentation with the latest flow.

These changes have not been deployed to Adobe Exchange production yet, they are going to be deployed today, @pru55e11 can you merge and deploy this on stage,so our QA can validate? and then deploy on prod later today or tomorrow.

Related Issue

https://jira.corp.adobe.com/browse/XCHG-15232

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[hellomadhur]

Description and images looks good.