Prior to this commit, the community memberlist was represented in a nested modal
which doesn't adhere to the designs. Rather, the section should render inside the
existing modal, requiring it to be refactored using a `StackView`.
This commit refactors the community profile popup so that the different content
sections ("Overview" and "MemberList") are rendered inside of the popup and can
be pushed onto and popped off a stack view.
The content components (newly introduced in this commit) `CommunityProfilePopupMembersList`
and `CommunityProfilePopupOverview` need to define a `headerTitle`, `headerDescription` and
if needed `imageSource` so they can alter the modal's header.
The same pattern might be used in other places of the modal if required.
Partially fixes#1959
Jonathan Rainville
Pascal Precht