Creator/Owner/Admin of a room with no PL event not shown in the People sidebar

### Steps to reproduce

1. Have a room with no `power_levels` event.
2. Open the People sidebar on the right
3. Observe:

even though "Me" created the room.

### Outcome

#### What did you expect?
Generally, rooms do not necessarily have an [`m.room.power_levels`](https://spec.matrix.org/v1.19/client-server-api/#mroompower_levels) event – the spec even makes explicit how this is to be interpreted.
So clients should be able to handle this case correctly and mark the creator of the room as such in the People sidebar, making their privileged position visible.

Like in rooms with a PL event, it should say `Admin` for pre-v12 rooms, and `Owner` for v12 rooms, like this:

#### What happened instead?
The room creator is not marked as such in the People sidebar, hiding their privileged position.

### Operating system

Arch Linux

### Browser information

Mozilla Firefox 152.0.4 (64-bit)

### URL for webapp

app.element.io

### Application version

Element version: 1.12.23 Crypto version: Rust SDK 0.18.0 (6fe03c1), Vodozemac 0.10.0

### Homeserver

matrix.org

### Will you send logs?

No

Start by reproducing the missing-power_levels case in the People sidebar and trace the code that determines a room member's privileged role. Check how the sidebar handles rooms without an m.room.power_levels event. Done means the creator is shown as Admin for pre-v12 rooms and Owner for v12 rooms, matching rooms with a power-levels event.

Written by the indexing model from the issue text.