chore: Upgrade salt, mega-evm version & update test_data

[flyq]

Summary

This PR upgrades the mega-evm + salt dependencies, updates chain execution/config wiring to match, and refreshes the repo’s bundled genesis + stateless test fixtures accordingly.

What changed

• Dependency upgrade
  • Bumped mega-evm / salt (and lockfile updates).
  • Adjusted core integration points in:
    • validator-core/src/chain_spec.rs
    • validator-core/src/executor.rs
• Genesis refresh
  • Updated genesis/genesis.json
  • Removed genesis/genesis-6342.json
  • Minor updates in README.md and bin/stateless-validator/src/main.rs to align with the new genesis handling.
• Test data refresh
  • Updated test_data/contracts.txt
  • Refreshed test_data/blocks/*.json
  • Added/removed corresponding stateless witness artifacts under test_data/stateless/witness/ (*.mpt, *.salt)

Commits included

• bf6ab63 — upgrade mega-evm & salt
• ad072a3 — update test data
• 1d64bcc — update genesis.json