[Master feature] True doc-level infinite scroll

[wassgha]

Master issue to track work on fixing up amp-next-page and adding true infinite scroll to it. Will be updated with more tasks as needed.

Replaces #14059

Task List

Fixing broken features

• amp-pixel preemptively firing event on fetch Next Page pageview GA event fired in <amp-pixel> while using with <amp-next-page> #25069
• Broken behavior on smaller documents <amp-next-page> needs enough text to trigger a scroll before the next page loads #14876
• Broken transitions to the first page on large viewports [amp-next-page] does not revert to original URL on large viewports #19823
• Lack of amp-analytics support (Allow amp-ad and amp-analytics to be rendered in amp-next-page articles. #15807 , amp-analytics calculates wrong scroll triggers for embedded shadow documents #18735 , and Issue using amp-analytics with Shadow DOM #20400 )
• Large bundle size because of dependence on v0 amp-next-page: Accidentally bundling v0.js #22357
• Interaction between the recommendation box and the AMP cache amp-next-page: Image URLs aren't rewritten from canonical to cache #15700

Adding new features

• End-to-end tests Add e2e tests for amp-next-page #24610
• Start v0.2 implementation
• Dynamic adoption of shadow mode Dynamic adoption of shadow mode #25630
• Communicate document changes to the viewer amp-next-page: "Active" document URL and sharing in viewer context #15819
• Better separators and transitions (TBD, Visual indication of "active" article in amp-next-page #15818 is partial)
• Better handling of sticky elements (✨Handling sticky, fixed and hidden elements in amp-next-page v2 #26106 )
• True infinite scroll phase 1
• True infinite scroll phase 2 (unloading, placeholding and reloading, ✨Implement infinite article loading on amp-next-page v2 #26296)
• Templating the recommendation box (✨<amp-next-page> v2 default and templated footers (more articles box) #26610 )
• Allow for history manipulation (minimally to be able to go back to the original article) [amp-next-page-v2] History manipulation #25553

[wassgha]

/cc @kristoferbaxter

[nainar]

@wassgha can this be closed?

[wassgha]

Yup!