Migrate to Interstitial for Trusted Book Provider read actions

[SivanC]

Closes #10561

Feature/refactor

Technical

Add new behavior to borrow API to redirect to an interstitial page in the case that a read/borrow action is requested on a non-IA provided edition. Also removes the existing toasts that are generated when using a direct provider read button link.

Testing

1. Click a read/borrow button for an edition provided by a trusted third party provider
2. Observe that you are now redirected to an interstitial page, and that you can observe the countdown timer, cancel the redirection, or immediately follow to the link.
3. Observe that there is no longer a toast on the original page after clicking the button.

Screenshot

Stakeholders

@mekarpeles

[SivanC]

There were a couple URLs that I wasn't sure behaved the same way as the standard read/borrow action URls that I haven't touched, those being the librivox template (because it's an audio link) and the direct provider preview link (uses the same URL as the regular read link did but not sure if we want the same behavior?)

[mekarpeles]

The Interstitial design / presentation needs a bit of work; some suggestions provided

[SivanC]

Marking as ready for review according to discussion from the community meeting. For some reason I am unable to get the template CSS to work on my end, but the lines that could be added optimally are $putctx('cssfile', 'interstitial') in templates/interstitial.html and .interstitial { padding: 15%; } in a new file static/css/components/interstitial.less

[jimchamp]

Thanks @SivanC!

I left some review notes, and am happy to merge this once those are addressed.

The main issues are:

1. Interstitial page needs some margins
2. Some aria attributes are no longer appropriate without toast messages
3. JS in template should be moved to Webpack (cancel link code is optional)

[jimchamp]

This isn't necessary for this PR, but noting that we may want to move this into Webpack in the future. This could be a good first issue, and the solution could be modeled on our recent cancel link changes (#9795).

Definitely not a blocker.

[SivanC]

@jimchamp Thanks for the detailed review! I'll take a crack tomorrow, haven't dived too deep into the JS side of things on the project so might shoot you some questions if I get stuck somewhere

[jimchamp]

Thanks for the quick turn-around, @SivanC! I'm going to make a small commit to remove my unhelpful comments, then merge. This is great!