Warn explicitly in the chat when `experimentalRustCrypto` is enabled and the kinds of bugs they might experience

Since we're probably unlikely to make a decision to remove it entirely we should write this. And we should remove it from the default.yml config or whatever

See https://github.com/the-draupnir-project/Draupnir/issues/1104 among other issues

We should also tell them about why an encrypted management room won't hide what commands are being used and also that for server acl, ban sync, and protections that dont' scan content, draupnir works fine in encrypted rooms without the encrypted device.