Rich bubble: scrollToAnchor + getAnchorRect

Adds a base getAnchorRect on ChatMessageBubbleContentNode, the rich-bubble
override (including titleHeight in details recursion), bubble-item
forwarding to content nodes, ChatControllerInteraction.scrollToMessageIdWithAnchor,
and a scrollToAnchor that lands the anchor at the top of the content area /
its line. Threads anchor/scroll params through ChatController and related
call sites.

submodules/TelegramUI/Sources/ChatHistoryListNode.swift

@@ -5064,7 +5064,7 @@ public final class ChatHistoryListNodeImpl: ListViewImpl, ChatHistoryNode, ChatH
         }
     }
     
-    func scrollToMessage(index: MessageIndex) {
+    func scrollToMessage(index: MessageIndex, offset: CGFloat = 0.0) {
         self.appliedScrollToMessageId = nil
         self.scrollToMessageIdPromise.set(.single(index))
     }