✨[amp-ad] Support new ad attribution reporting API

[calebcordry]

Description

https://developer.chrome.com/docs/privacy-sandbox/attribution-reporting/

• Introduce new browserAdConversion functionality to amp-ad-exit
• Support feature rollout monitoring with ATTRIBUTION_REPORTING_STATUS macro
• Add origin trial tokens
• Add feature policy to 3p fallback ad frames

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions.