Inconsistencies on room invite badges

### Steps to reproduce

When receiving a room invite in a space, we use red dots inconsistently throughout:

1. The invites room header uses a number in a red dot.
2. The room component in the room list is an alarmist exclamation mark.
3. Some disappear on hover, some don't.
4. I did not capture/notice what the space panel is doing, but we should sanity check when actioning quick wins here.

### What happened?

See above.

### What did you expect?

1. Something less alarmist than an exclamation mark (should we just use a red dot? Reduce size by a few px?)
2. Hover states to behave consistently.

### Operating system

_No response_

### Browser information

_No response_

### URL for webapp

develop.element.io

### Have you submitted a rageshake?

No