issue: https://linear.app/comm/issue/ENG-3933/flatten-the-list-of-items-to-render-in-communitydrawercontent
CommunityDrawerItemCommunity and CommunityDrawerItemChat are no longer needed:
CommunityDrawerItemCommunity existed mostly to take care of some styles, but because of changes needed to remove nested FlatLists, the styles are now handled differently - by the
`itemData.itemStyle` prop.
CommunityDrawerItemChat existed to hold the expanded state for items on deeper levels, but this state (as discussed in ENG-3934 ) is now handled by CommunityDrawerContent.
Because the `expanded` state for all items is now handled by `CommunityDrawerContent`, `openCommunity` state is no longer needed. We can check which community is open by
`expanded.includes(id)`. `expanded` initial state is `communitiesSuffixed.length === 1 ? [communitiesSuffixed[0].id] : []`, because if there is only one community it is supposed to be open by
default. Communnity items still need a different function for `toggleExpanded` though, because when one community is opened, the other one collapses automatically.