Implement Fallback for Blocked demdex.net Requests

[shammowla]

Summary

Added fallback mechanism to use configured edge domain when demdex.net requests fail. This improves reliability when users have ad blockers or network restrictions that block third-party endpoints.
Changes

Added detection of demdex.net failures in network requests
Implemented fallback to edge domain
Added test coverage

Testing

Verified behavior with:

New functional test suite (demdexFallback.js)

Description

Related Issue

Motivation and Context

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (non-breaking change which does not add functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA or I'm an Adobe employee.
• I have made any necessary test changes and all tests pass.
• I have run the Sandbox successfully.