InlineHelp: Make requests cancelable

[retrofox]

It'd be nice if the enqueue requests can be cancelable in order to avoid hitting the API unnecessarily.

Steps to reproduce

1. Locate the Get Help... section in the customer home page (http://wordppress.com/home/<your-site>)
   OR open the inline help clicking on the FAB icon (any another page)

Customer home

Inline help

2. Open the network tab of your developer browser
3. May you'd like to filter the requests by search term

4. Type a term in the search input element, wait for the threshold ends, and do again, and so on.

What I expected

Run only one (the last one) request and cancel the rest of them

What happened instead

The client performs all requests, even those that won't be used.

[getdave]

Is this related to the situation whereby if you search for some nonsense like ;;;;pppp;;;; then it takes ages for the request to complete? Also is this related to the need to upgrade to a proper data layer implementation?

[retrofox]

Is this related to the situation whereby if you search for some nonsense like ;;;;pppp;;;; then it takes ages for the request to complete?

I'm not totally sure. I think that isn't exactly the same issue but a matter of defining a smaller request timeout?

Also is this related to the need to upgrade to a proper data layer implementation?

Maybe yes, it would require to connect with the data-layer.

[getdave]

Consider following cancellable promise wrapper approach as used in Automattic/jetpack#15228

[github-actions]

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