[52555] Add searchbar to Submenu component

[HDinger]

ToDo

• Add an option to display a "search" input the SubMenu component
  • Extract logic of filtering used for projectAttribute list (in the project settings) into a reusable controller
  • Use that generic controller inside the SubMenu component
  • When there are no results, show a generic info text
• Enable the search functionality on the project list page

cleanup

• I moved the existing filters.controller to a separate filter folder and renamed it to filters-form.controller

https://community.openproject.org/projects/openproject/work_packages/52555/activity

[oliverguenther]

In the current implementation used in work packages, groups without hits are hidden:

This is no longer the case:

I'm aware that the implementation you chose might make it quite hard to allow this to happen in the new groups as well, I just wanted to raise it.

Code-wise, LGTM 👍

[oliverguenther]

We'll accept the difference in behavior for now, and check with the designers