Remove repetitive code at Contact, on relative velocity calculation

[diogomene]

While analyzing the Contact class source code using Qodana, a duplication was identified in the calculations of the relative velocity at the contact point between two bodies:

matrix.zeroVec2(dv1);
matrix.plusVec2(dv1, vB);
matrix.plusVec2(dv1, matrix.crossNumVec2(temp, wB, vcp1.rB));
matrix.minusVec2(dv1, vA);
matrix.minusVec2(dv1, matrix.crossNumVec2(temp, wA, vcp1.rA));

This set of instructions is repeated three times across the methods of the Contact class, with no apparent occurrences in other classes. Duplicated code can increase complexity for future maintainers, making the code harder to read and modify. Any changes to the calculation logic would require updates in multiple locations, raising the likelihood of errors or inconsistencies.

To address this issue, I suggest extracting the duplicated instructions into a dedicated method within the Contact class. Centralizing these operations would make the code cleaner, easier to read, and less prone to errors, as any modifications would only need to be made in a single location. This approach would improve maintainability and ensure consistency throughout the code.