State-reset and security mitigations.

Upgrade Ruma to present.

The following are intentionally benign for activation in a later commit:

- Hydra backports not default.
- Room version 12 not default.
- Room version 12 not listed as stable.

Do not enable them manually or you can brick your database.

Signed-off-by: Jason Volk <jason@zemos.net>

.cargo/config.toml

@@ -0,0 +1,2 @@
+[env]
+RUMA_UNSTABLE_EXHAUSTIVE_TYPES = "true"