feat: add create cluster tests

[varex83]

Summary

Ports the Go TestCreateCluster test suite to Rust, covering all major create_cluster flows end-to-end, and fixes several correctness issues uncovered in the process.

New tests (crates/cli/src/commands/create_cluster.rs)

A shared run_test_create_cluster helper drives all test cases, mirroring the Go test loop. Each case exercises run() against a temp directory and asserts:

• the command succeeds (or returns a specific error)
• the generated cluster-lock.json passes verify_hashes() and verify_signatures()
• all distributed validators have unique public keys
• deposit-data amounts match expectations
• CLI output and produced file tree match golden snapshots

Test cases covered:

Test	Notes
simnet	4-node simnet cluster
goerli	Goerli network, 3-node
custom_testnet_flags	Custom chain ID / fork version / genesis timestamp
custom_target_gas_limit	Non-default target_gas_limit
solo_flow_definition_from_disk	Definition loaded from a local JSON file
solo_flow_definition_from_network	Definition served over HTTP (wiremock)
splitkeys	--split-existing-keys, keys generated in a temp dir
splitkeys_with_cluster_definition	Split keys combined with a pre-existing definition
four_partial_deposits / two_partial_deposits	Multiple deposit amounts per validator
with_fee_recipient_and_withdrawal_addresses	Custom fee-recipient + withdrawal addresses
validate_def	Invalid definition triggers expected error

Golden files live in crates/cli/src/commands/testdata/ and can be regenerated with UPDATE_GOLDEN=1 cargo test.

Bug fixes

• create_cluster::run — call def.set_definition_hashes() before proceeding with key generation; the hashes were previously unset, causing verify_hashes() to fail.
• definition.rs deserialization — validate that num_validators == validator_addresses.len() for schema versions v1.5–v1.10; add #[serde(default)] to fee_recipient_address, withdrawal_address, and compounding so older JSON examples without those fields still deserialize correctly.
• lock.rs no_registration check — remove the zero-fee_recipient guard. The Go reference uses len == 0 (missing field), not the zero Ethereum address; a legitimately zero fee-recipient is valid. Only an all-zero BLS signature or pubkey indicates a missing registration.
• cluster-definition-005.json — fix malformed timestamp (stray spaces around : separators).

Test plan

• cargo test -p pluto-cli passes with all new test cases green
• UPDATE_GOLDEN=1 cargo test regenerates golden files without diff
• Existing tests unaffected