Add simple and intermediate Integral Calculus datasets

[joesharratt1229]

Description

I would like to propose two dataset generators for integral calculus questions:

1. Simple integral calculus

Focused on basic definite integration tasks. Solve integration problems involving simple polynomials. E.g $\int_{0}^{1} x^2 , dx$

• Implementation - of SimpleIntegrationConfig class and SimpleIntegrationDataset

2. More complex integration problems.
Focused on more complex integration tasks. Specifically on integration by parts and integration by substitution. Evaluated over limits.

• Implementation - of IntermediateIntegrationConfig class and IntermediateIntegrationDataset

Tasks

• Create configuration and dataset classes for both problems

• Implement unit tests for deterministic generation, correct structure, and verification logic.

• Ensure code aligns with existing repository conventions (e.g., ProceduralDataset base class, register_dataset).

• Document configuration parameters, usage examples, and test coverage.