Major Description
`GlobalRegistration` is a global listener that requires to be aware of all changes in a cluster and thus is very annoying: We don't want a single James server to receive all events in the cluster as it is not scalable.
This listener is keeping track of MailboxPath changes in order to update indexed content accordingly.
This work is not at all required if indexing is performed using `MailboxId` which is immutable in the first place.
Rewrite `mailbox/tools/indexer` code to rely on MailboxId.
Remove `GlobalRegistration` and related tests from the code base.