Whenever a cluster is removed from Envoy via xDS update, the ThreadLocalStore::Scope will be cleaned up, and the corresponding CentralCacheEntry objects will also be deleted.

However, there are also TlsCacheEntry objects for each thread, and those will continue to reference any stats that were created for clusters, and there does not appear to be any mechanism to reclaim those map entries or GC away the stat objects themselves, which are kept alive by a shared_ptr.

I believe a cleanup could be engineered by post()ing a GC request to each thread at the time the Scope is deleted.