Extension Analytics V1

[zhouyx]

This is a tracker issue for #6417

• insert <amp-analytics> for extension (Normalize jank rate to a likelihood metric. #7490)
• Limit support for certain eventType (Whitelist certain eventType and scope selector for analytics in scope #8389)
• Apply replacement on selector/selectorMethod of the config (Whitelist certain eventType and scope selector for analytics in scope #8389)
• Allow extension to load analytics extension // Pend on feature request
• Refactor customEventTracker. Change it from mapping an eventType to observer, to mapping an [eventType and extension] to observer (Extension analytics: only trigger custom event for its target #8304) // Decide not to do this
• Add restriction on url replacement (Use whitelist to restrict urlReplacement for scoped analytics element #8360)
• Remove injectActiveViewAmpAnalyticsElement function (remove usage of #injectActiveViewAmpAnalyticsElement function #8628)
• Support selector to analytics customEvent (Analytics: customEvent trigger add support to selector #9285)
• Enable extension to define their own customEvent (Create customEventReporter #10163)
• Documentation (Readme for components to implement analytics #11276)

[rudygalfi]

@zhouyx Can you close? Let's document the remaining items that aren't done, but which will be considered upon request.

[zhouyx]

Closing this for now. Will create separate issue to address the customEventTracker issue