FileSet objects created by PDF Issue ingest need more descriptive titles

[ebenenglish]

User story
As an admin user
When I create a new NewspaperIssue work via the admin UI
And I upload a PDF as an attachment to that work
The FileSet children of NewspaperPage objects that are created representing the pages of the issue
Should have descriptive, human-readable titles
So that they display in a user-friendly way in the Universal Viewer

Discussion
By default, FileSet children of Page objects created via PDF Issue upload are given the generic titles like:

3ac3e797-1c7f-4c75-935b-5df0f558521c-page2.tiff

Which makes for less-than-ideal UX, as these long titles are essentially gibberish, and are unwieldy when viewing the list of files as thumbnails or search results in the Universal Viewer.

We should give these FileSet objects the same title as the parent NewspaperPage.

(Possibly unpopular/controversial assertion, more discussion needed.)

This ticket will be complete when
Automatically-created Page objects have more descriptive titles that allow them to be more easily distinguished from each other.

TO-DO
See if this is also an issue with NDNP batch-ingested content.