chore: Upgrade mega-evm dependency from v1.2.0 to v1.2.1

[flyq]

Changes

• Dependency Update: Updated mega-evm from v1.2.0 to v1.2.1
  • Updated dependency reference in Cargo.toml
  • Updated lock file with new git revision: fa3b03c1a524d90eaf6ec338023e3269b94cec9c

https://github.com/megaeth-labs/mega-reth/pull/1281
mega-evm v1.2.1 fixes a bug in the inspector that could affect the evm trace in the validator-core executor.

• Code Cleanup: Minor import organization improvements
  • Reorganized imports in validator-core/src/database.rs to follow Rust conventions (external crates before internal modules)
  • Improved import grouping in validator-core/src/validator_db.rs for better readability

Files Changed

• Cargo.toml - Updated mega-evm dependency version
• Cargo.lock - Updated dependency lock with new revision
• validator-core/src/database.rs - Import ordering cleanup
• validator-core/src/validator_db.rs - Import formatting improvements

Testing

• Verify project builds successfully with new mega-evm version
• Run existing test suite to ensure compatibility
• Validate stateless validator functionality with updated dependency