Make Buttons and Dropdowns Turbo 8 friendly

[Robin481]

Depends on this being completed: #752

Turbo 8 adds Link-Preloading. This works perfecty fine for normal links but not for e.g. The People dropdown because those probably aren't normal links. Some dropdown libraries have a option to display the elements as links. Maybe ours has that.

TODO:

• Check which buttons, dropdowns or actual links that don't work with Link-Preloading yet
• Try to fix as many of those wherever possible
• Make sure performance doesn't become an issue (e.g. In the People Dropdown scrolling over "all" the people when looking through the list will then send a request each which might be a bit too much)

[RandomTannenbaum]

ToDo

• Check links in application and document which do not work yet with link preloading -> especially check slim select dropdowns
• Fix those that are possible
• Smoke Test
• Review

[RandomTannenbaum]

ToDo

• Find good timeout for link prefetching in people dropdown
• Check possibilities for prefetching on-focus
• Check performance impact on server
• Fix language selection
• Re-disable link prefetching in dev before merging ticket
• Update version number