In D4434, there were certain changes made that made D4481 broken since `ChatMessageList` was refactored. This diff brings `ChatMessageList` up to date and out of a broken state. (This is also the reason D4697 and D4698 were failing builds, since the old `ChatMessageList` code from D4481 was still in my stack because it wasn't landed prior to D4434.) This is a diff in a stack of diffs that will resolve the timestamp bug, related Linear issue [[ https://linear.app/comm/issue/ENG-1266/timestamp-appears-below-chatinputbar-on-web | here ]]. The purpose of this diff is just to fix `ChatMessageList` since it was in a broken state for me, the rest of the tooltip diffs will come later in the stack.