[mypy] Annotates other/scoring_algorithm (#5621)

* scoring_algorithm: Moves doctest into function docstring so it will be run

* [mypy] annotates other/scoring_algorithm

* [mypy] renames temp var to unique value to work around mypy issue in other/scoring_algorithm

reusing loop variables with the same name and different types gives
this very confusing mypy error response.

pyright correctly infers the types without issue.

    ```
    scoring_algorithm.py:58: error: Incompatible types in assignment
    (expression has type "float", variable has type "List[float]")
    scoring_algorithm.py:60: error: Unsupported operand types for -
    ("List[float]" and "float")
    scoring_algorithm.py:65: error: Incompatible types in assignment
    (expression has type "float", variable has type "List[float]")
    scoring_algorithm.py:67: error: Unsupported operand types for -
    ("List[float]" and "float")
    Found 4 errors in 1 file (checked 1 source file)

```

* scoring_algorithm: uses enumeration instead of manual indexing on loop var

* scoring_algorithm: sometimes we look before we leap.

* clean-up: runs `black` to fix formatting