Remaining issues after #280

[ShadowJonathan]

https://github.com/matrix-org/mjolnir/pull/280 was merged for time pressure, but afaik there's two more things to be looked at;

• The PR introduced requiredStatePermissions, these announce the permissions a protection would likely need. Currently these only work on a manual !verify command after startup, as protections are only added enabled the startup verify. (And it will only consider enabled protections for the permissions they need)
• The PR currently uses an hourly bucket, but it was suggested to use a sliding token bucket. This has to be added.