Room aliases list doesn't take into account multiple m.room.aliases states

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The [Room.update_aliases](https://github.com/matrix-org/matrix-python-sdk/blob/master/matrix_client/room.py#L416) method does not take into account that there can be multiple `m.room.aliases` states. Because room aliases from separate HSes are in separate `m.room.aliases` states (with the HS name as the state key), this means the `update_aliases` function will actually set the aliases list to only contain the aliases from one HS, disregarding the others.

Example (the code should list all aliases for Matrix HQ):
```
>>> client.rooms['!cURbafjkfsMDVwdRDQ:matrix.org'].update_aliases()
True
>>> client.rooms['!cURbafjkfsMDVwdRDQ:matrix.org'].aliases
['#matrix:utzutzutz.net']
```

Comienza en matrix_client/room.py, en Room.update_aliases, y reproduce después el ejemplo para la sala Matrix HQ. Comprueba cómo se gestiona cada estado m.room.aliases y verifica que la lista de alias resultante incluya alias del estado de cada homeserver, no solo de uno.

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