Admin API - Users' message event usage statistics

This issue has been migrated from [#11871](https://github.com/matrix-org/synapse/issues/11871).

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Are there any plans to expand the pre-existing admin API offerings for [statistics](https://matrix-org.github.io/synapse/develop/admin_api/statistics.html)?

E.g. While the pre-existing "[Users' media usage statistics](https://matrix-org.github.io/synapse/develop/admin_api/statistics.html#users-media-usage-statistics)" offering covers media, it doesn't cover message events. I'm thinking about this through a lens of:

- Keeping track of users and/or rooms that consume the most resources (e.g. top 10 users/rooms).
- Yes a media datum will typically be larger than a message event, but if there are users and/or rooms that are emitting large quantities of message events (e.g. IoT bots), that message event volume could build up.

Edit (2022-03-24): It [appears](https://github.com/matrix-org/synapse/issues/9602) as though some functionality relating to this had existed.