fix(messagesStore) - clean conversation history for participants in call

[Antreesy]

☑️ Resolves

• Fix delete chat messages - still visible to 3rd party despite cleared the history.. indicator #10298

Solution might be a bit overkill, so here are some explanations:

• System message history_cleared will be the first one in conversation by definition, so only previous messages should be cleared
• Depending on internet connection, or after conversation switching - there could be a new messages after clearing, so we can't purge the whole room, because it also could clear new ones.
• When scroll to the top and fetch - system message will be last processed and first known, so no mutations should occur

🖼️ Screenshots

clear-history.webm

🚧 Tasks

• Code review

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not required
• 📘 API documentation in docs/ has been updated or is not required
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required
• 🔖 Capability is added or not needed

[nickvergessen]

/backport to stable27

[nickvergessen]

/backport to stable26

[nickvergessen]

/backport to stable25

[DorraJaouad]

Tested ✅