[Task] Add a method to resolve send failures due to an identity change and retry sending.

[pixlwave]

Part of element-hq/element-meta#2500 and likely requires #3837

Once the error is surface from #3793 we need a way to allow a user to resolve the error and retry sending. This can be done in the following way:

For "verification violation" there is a new UserIdentity::withdraw_verification that you can call, then retry sending. (you can also blacklist if you prefer via Device::set_local_trust)
⁦And same the error gaves you all the problematic user_id, so you can just iterate, withdraw_verification then resend