Revert "analytics: bail out for detached targets"

[samouri]

Reverts #32637

Potential "fix" to ampproject/error-reporting#54.
Setting this up in case we want to eventually merge, we'll have the CI predone.

[samouri]

Did more digging. I was very wrong. Most of the flows do work when the node is detached. Both element.ownerDocument and element.ownerDocument.defaultView both work on detached nodes.

The bug I was trying to address was this: .

I traced through the mangled names in amp-form and amp-analytics, the failure flow is this:

1. triggerAnalyticsEvent(...)
2. this.findRoot(target)
3. getParentWindowFrameElement(target)
4. getTopWindow((target.ownerDocument||target).defaultView)) --> win.__AMP_TOP

Other notes:

• The error we are seeing is that we are trying to read a property on undefined. Working backwards this means that the .defaultView is evaluating to undefined.
• When called on a Document, defaultView can never be undefined. It is always either Window|null. This means that target.ownerDocument||target evaluates to a non Document.
• element.ownerDocument can only be null if the element is itself a document, which is exactly what this is expression is built for. This means that target must not have been a Node.

Since the original case was calling analytics on a HTMLIframeElement thats also impossible to ever happen. Except during the one commit where I was testing out targeting an AmpDoc which I reverted before merging 🤕. I didn't realize the console error was newly introduced, and after a closer look at the original error the followup fix should have been somewhere in ampdoc-impl.getAmpdocIfAvailable