Use new AvatarManager also for ContactItems

...lin/org/briarproject/briar/desktop/contact/ContactItem.kt

...org/briarproject/briar/desktop/contact/ContactItemView.kt

...riarproject/briar/desktop/contact/ContactItemViewSmall.kt

...lin/org/briarproject/briar/desktop/contact/ContactList.kt

...riarproject/briar/desktop/contact/ContactListViewModel.kt

...g/briarproject/briar/desktop/contact/ContactsViewModel.kt

...n/org/briarproject/briar/desktop/contact/ProfileCircle.kt

...oject/briar/desktop/conversation/ConversationViewModel.kt

...n/org/briarproject/briar/desktop/forums/ThreadItemView.kt

...ect/briar/desktop/forums/sharing/ForumSharingViewModel.kt

...oject/briar/desktop/introduction/IntroductionViewModel.kt

.../org/briarproject/briar/desktop/utils/PreviewDataUtils.kt

...org/briarproject/briar/desktop/contact/ContactItemTest.kt