Refactor `execute_finalized_block` operations logic refactor.

Refactor `execute_finalized_block` [operations](https://github.com/casper-network/casper-node/blob/1f511ec34bda10e0508270931d2eff2bf6d98ff2/node/src/components/contract_runtime/operations.rs#L57) 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