Use `Default::default()` to construct `()` as a test scoring param

Use `Default::default()` to construct `()` as a test scoring param

In bindings, we can't use unbounded generic types, and thus have to
rip out the `ScoreParams` and replace them with static
`ProbabilisticScoringFeeParams` universally. To make this easier,
using `Default::default()` everywhere allows the type to change out
from under the test without the test needing to change.