amp-iframe allowing multiple sources

### Description

Increase the number of amp-iframe elements or sources allowed on a single AMP page to provide publishers with more flexibility and opportunities to monetize their content. Currently, AMP restricts the use of amp-iframe elements to ensure optimal page performance and user experience. However, some publishers have expressed a desire for more amp-iframe elements to be allowed on a page, particularly for displaying ads and third-party content.

While increasing the number of amp-iframe elements could potentially impact page performance and loading times, this could be mitigated by providing clear guidelines and best practices for using amp-iframe elements and ensuring that they are used sparingly and appropriately. By balancing the potential benefits and drawbacks, an increase in the number of amp-iframe elements could be a valuable feature request for publishers looking to enhance their content offerings and monetization strategies on AMP pages.

### Alternatives Considered

Without impacting the performance that is expected from AMP pages, is there a possibility to upgrade the amp-iframe component so that it could take a list of URLs that needs to run within the 5s execution time?

### Additional Context

_No response_