[VSA] - Fix UX issues with multiselect dropdown on group level

Problem

On group-level VSA users can select multiple projects from the dropdown. However, there are some UX issues with the dropdown when trying to select multiple projects:

• The dropdown is closed when an item gets selected
• The search input in the dropdown isn't visible anymore when a previously scrolled to the bottom (user has to scroll back to top)

group_level_vsa_multiselect_project_dropdown

Prooposal

We should introduce the following changes to the dropdown:

• When multiselect is enabled, the dropdown should remain open when a user selects an item
• The dropdown is only closed when the user clicks away
• Once the user clicks away, search input is cleared and the we scroll back to the top