Move @Composables into separate files

src/main/kotlin/org/briarproject/briar/desktop/Main.kt

...rg/briarproject/briar/desktop/contact/AddContactDialog.kt

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

...arproject/briar/desktop/contact/ContactDrawerMakeIntro.kt

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

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

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

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

...otlin/org/briarproject/briar/desktop/contact/Identicon.kt

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

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

...otlin/org/briarproject/briar/desktop/conversation/Chat.kt

...ar/desktop/conversation/ChatHistoryConversationVisitor.kt

.../org/briarproject/briar/desktop/conversation/ChatState.kt

...g/briarproject/briar/desktop/conversation/Conversation.kt

...rproject/briar/desktop/conversation/ConversationHeader.kt

...arproject/briar/desktop/conversation/ConversationInput.kt

...sktop/conversation/ConversationMessageHeaderComparator.kt

...rproject/briar/desktop/conversation/PrivateMessageView.kt

.../briarproject/briar/desktop/conversation/SimpleMessage.kt