[BUG] Proxies may register the same entity multiple times

[wilyle]

Description

When the cartographer gets a new mapping, it will try to create or update proxies for each entity in the mapping, even if it's already being tracked. This can result in multiple registrations in a proxy for the same entity, or even multiple proxies tracking the same entity

Acceptance criteria

• Proxies should correctly handle register requests for duplicate entities OR cartographer should not submit register requests for already tracked entities