feat: [BBND-1370] Migrate MP to Ethers 6

[rubenbermejo3]

Description

Migrated the Mass Payout SDK from Ethers v5 to Ethers v6 to ensure compatibility with the latest ecosystem standards and security updates. This migration addresses critical API changes, deprecations, and structural differences between versions while maintaining full backward compatibility for existing functionality.

Key changes made:

• Updated all Ethers v5 syntax to v6 equivalents (.address → await getAddress(), .deployed() → waitForDeployment(), etc.)
• Fixed event assertion patterns in test suites to work with Ethers v6's position-based argument handling
• Updated import statements and dependency versions across contracts and SDK packages
• Resolved staticCall result structure changes from object-based to array-based returns
• Fixed TypeScript compilation errors related to typechain and contract interactions

Motivation: Ethers v6 introduces breaking changes that required systematic updates to maintain functionality and security. This migration ensures the Mass Payout SDK remains compatible with modern tooling and avoids deprecation warnings.

Type of change

• Bug fix 🐞
• New feature ✨
• Breaking change 💥
• Documentation update 📖
• Refactor 🔧

Testing

Test Results

• Total tests: 615
• Passing: 615 ✅
• Failing: 0 ✅
• Node version tested: 22

Verification Steps

1. Run npm run test in packages/mass-payout/contracts → All 615 tests pass
2. Run npm run test:coverage → Coverage maintained without reduction
3. Run npm run lint:sol → No new Solidity linting warnings
4. Verify contract deployment scripts work with new Ethers v6 syntax
5. Test SDK transaction adapters with updated Ethers v6 APIs

Test Environment:

• Hardhat framework with Ethers v6 integration
• TypeScript compilation passes without errors
• All contract interaction patterns updated to v6 standards

Checklist

• Style Guidelines followed ✅
• Documentation Updated 📚
• Linters - No New Warnings ⚠️
• Local Tests Pass ✅
• Effective Tests Added ✔️
• No reduction of Coverage ✅

[hedera-eng-infrastructure]

✅ Snyk checks have passed. No issues have been found so far.

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