Change defaults for group notification settings

### Your use case

- Currently by default Notifications are only enabled for direct messages and not for group messages.
- For users coming from Signal or other messengers this is confusing because both on Signal as well Telegram group notifications are enabled by default
- I have heard from different people comments like "Élément is nice, but the notifications don't work" / "I miss new messages" and in the end it was because this group notifications was disabled by default
- Also on start there is no tutorial or something similar, where this default is mentioned or explained.

Proposal:
- Enable notifications for groups by default for new installs

### Have you considered any alternatives?

An alternative would be an intro screen where users can configure important settings on first start.

### Additional context

_No response_

Start by identifying which Element client repositories implement the default group notification setting for new installs; this meta issue names no files or tests. Compare the current behavior with the proposal, then verify that group notifications are enabled by default for new installations without changing existing users' settings.

Written by the indexing model from the issue text.