fix(MessagesList): soft update groups when fetching old messages

[Antreesy]

☑️ Resolves

• Fix regression from Feat(MessagesList): Soft update messages list AND add sticky date separator. #11592 🥲

Let's assume we have messagesGroup {6} from one author with ids [6..10]
When fetching old messages, new group {1} is compiled for the same author, and covers messages [1..10]
As starting id is different, groups won't match and both remain in the list

🖌️ UI Checklist

Follow-up: move grouping logic to composable and add test coverage?

🏁 Checklist

• 🌏 Tested with Chrome, Firefox and Safari or should not be risky to browser differences
• 🖥️ Tested with Desktop client or should not be risky for it
• ⛑️ Tests are included or not possible

[DorraJaouad]

Nice catch btw

[DorraJaouad]

Tested 😨