Refactor `execute_finalized_block` operations logic refactor.

[devendran-m]

Refactor execute_finalized_block operations logic for maintainability and testability.

As a
Casper Node Developer I want to
refactor the execute_finalized_block operations logic into a modular and testable structure
So that;

• it is easier to maintain and understand
• we reduce procedural complexity
• we can write focused, reliable unit tests
• we can enable more granular and formal test coverage
• we future-proof the logic for changes to the execution pipeline