Meaning of `RoomFilter` with omitted `account_data`, `ephemeral`, `state` or `timeline` fields is unclear

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**Link to problem area**: https://spec.matrix.org/v1.3/client-server-api/#post_matrixclientv3useruseridfilter, definition of `RoomFilter`

**Issue**

`rooms` says:

Name | Type | Description
-- | -- | --
rooms | [string] | A list of room IDs to include. **_If this list is absent then all rooms are included_**. This filter is applied before the filters in ephemeral, state, timeline or account_data

(emphasis mine).

The other fields do not describe the meaning of the filter if they are omitted.

Name | Type | Description
-- | -- | --
account_data | RoomEventFilter | The per user account data to include for rooms.
ephemeral | RoomEventFilter | The events that aren’t recorded in the room history, e.g. typing and receipts, to include for rooms.
state | StateFilter | The state events to include for rooms.
timeline | RoomEventFilter | The message and state update events to include for rooms.

Noticed in https://github.com/matrix-org/synapse/issues/13648

Read the RoomFilter definition in the Client-Server API section linked in the issue, including the existing rooms description and the account_data, ephemeral, state, and timeline entries. Clarify the specification text so the behavior of each omitted field is explicit, and confirm the updated descriptions consistently explain the resulting filter behavior.

Written by the indexing model from the issue text.