Remove/justify clone() across the codebase

[lferrigno]

Campaign: Remove/justify clone() across the codebase

We want to reduce unnecessary clones in hot paths and make intentional clones explicit.

Goals

• Every clone() must be reviewed.
• If a clone is removed → commit the change and check it off here.
• If a clone is kept → add a comment above the line with
  // ok-clone: <reason>.

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Sub-issues

• VM & execution (crates/vm/**)
• Sequencer / L2 core (crates/l2/**)
• Networking P2P (crates/networking/p2p/**)
• Networking RPC (crates/networking/rpc/**)
• Blockchain core (crates/blockchain/**)
• Storage & trie (crates/storage/**, crates/common/trie/**)
• Common types/serde (crates/common/types/**, crates/common/serde_utils.rs)
• CLI/tooling/docs (cmd/**, tooling/**, docs/**)

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Process

1. Locate all clone() calls.
2. Classify:
   • Unnecessary → refactor to avoid copying (&T, Arc<T>, Cow, copied(), etc).
   • Required → keep and mark with // ok-clone: <reason>.
3. Submit small PRs per subsystem.

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Examples

// ok-clone: needed to increment Arc refcount
let x = arc_value.clone();

// ok-clone: async move requires owned value
tokio::spawn(do_work(config.clone()));

// ok-clone: serde requires owned String
let json = serde_json::to_string(&data.clone())?;