fix: anvil --fork-url with --load-state

[yash-atreya]

Motivation

Using both --fork-url and --load-state together can lead to various RPC issues due to the underlying ForkedStorage, ForkedDatabase and fork_db::SharedBackend getting out of sync while loading from the state file.

While this feature is highly prone to API misuse and errors, it can still be improved.

Solution

WIP