Update copy UI for citation modal

[thatbudakguy]

Closes #1335

This PR abstracts the controller that handled copying on the code snippets modal so that it can work for both the citation modal and code snippets modal, and then updates the UI for the citation modal to match.

Geoblacklight's own clipboardController doesn't include enough features to do this, but we can't redeclare a stimulus controller with that name, so the name was changed to clipboardCopyController. We could explore adding this functionality to Geoblacklight's version later.

[dnoneill]

Is there a reason for copying we aren't using the copy stimulus control from geoblacklight?

[thatbudakguy]

Yes – what I meant above by

Geoblacklight's own clipboardController doesn't include enough features to do this

Is that it doesn't support changing the target element to copy dynamically, which happens when you switch tabs on the code snippet modal.

It also expects an alert element to exist to update when you copy; we change the button text instead.