Improve caching of Annotations-data, by using a `Map`, in the API
Improve caching of Annotations-data, by using a `Map`, in the API

Rather than caching only the *last* `PDFPageProxy.getAnnotations` call, and having to handle the intent separately, we can instead implement the caching in exactly the same way as done in the `PDFPageProxy.{render, getOperatorList}` methods.

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