Lazy loading for tiles view

[kulmann]

Description

Our list views for files and folders (ResourceTable) has a lazy loading mechanism: rows that are not in the current viewport have a simplified DOM (a very simple skeleton loader effect) which only gets replaced with the actual cell contents when the respective row scrolls into view and the user stops scrolling for at least a few milliseconds. Our tiles view currently doesn't have it. As a result the DOM gets quite complex if you display a few hundred or thousand tiles (although the DOM of a file is already simpler than the DOM of a table row).

We want to have the lazy loading for the tiles view as well (see Value section below).

Will also improve #10578 (well... the less tiles are loaded the better it will be. Having all tiles loaded will not be the improved situation anymore of course).

User Stories

• As a user I want my photo gallery to load as fast as possible so that I can start scrolling through photos as early as possible.

• As a user I want don't want to have an input-delay when selecting files in the tiles view so that I have the feeling that my UI is snappy.

Value

Snappy UI due to:

• Shorter initial render duration, especially for large pages (if pagination page size is set to 500 or more)
• Less input-delay when selecting files in the tiles view

Acceptance Criteria

• introduce lazy loading to the tiles view
• make it the same look and feel like for the list views (table)

Definition of ready

• Everybody needs to understand the value written in the user story
• Acceptance criteria have to be defined
• All dependencies of the user story need to be identified
• Feature should be seen from an end user perspective
• Story has to be estimated
• Story points need to be less than 20

Definition of done

• Functional requirements
  • Functionality described in the user story works
  • Acceptance criteria are fulfilled
• Quality
  • Code review happened
  • CI is green (that includes new and existing automated tests)
  • Critical code received unit tests by the developer
• Non-functional requirements
  • No sonar cloud issues