core: Add tests for EIP-7702 authorization validation and application

[MozirDmitriy]

This pull request adds unit tests for the validateAuthorization and applyAuthorization
functions in core/state_transition.go. These functions are critical components
of the EIP-7702 implementation, which allows accounts to delegate code execution
to other accounts.

The tests cover:

• Chain ID validation to prevent replay attacks across networks
• Nonce validation to prevent transaction replay
• Nonce overflow protection
• Code validation to prevent setting delegations on contract accounts
• Proper delegation code setting and clearing
• Gas refund handling for existing accounts

While the EIP-7702 functionality has integration tests in blockchain_test.go and
transaction pool tests in legacypool_test.go, these unit tests provide more
focused coverage of the core authorization validation and application logic.