When `eth_unsubscribe` is received in the proxy, ensure this request is forwarded through on the correct socket (the same socket that was used for the corresponding `eth_subscribe`).
Move subscription handling for `eth_subscribe` and `eth_unsubscribe` to RpcModifiers (in `rpc-manager` package).
For each `eth_subscribe` request, a new `RequestManager` is created. Since the endpoint property on the proxy class was updated to be a provider, the same provider was being assigned to each new `RequestManager` and thus creating multiple event handlers for each subscription created. To circumvent this, we are now creating a new provider for each `RequestManager`.
Co-authored-by: Pascal Precht <pascal.precht@googlemail.com>