feat: Preview Proxy should render the page with the content from DA

[andreituicu]

Draft PR, because I'm not fully sure yet, still thinking about it, but don't want to loose the work in progress.

Description

Preview Proxy should render the page with the content from DA

Related Issue

Motivation and Context

There is currently no service that can return a rendered version of the content, as if it was previewed, but without doing the actual preview.

This PR attempts to do this, but with a few differences from how the UE path does it:

1. Don't add any instrumentation code
2. Reuse more of the information coming from the page, instead of trying to rebuild everything from scratch.

How Has This Been Tested?

Unit tests, but needs more testing.

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.