Fix EDM DPM Solver Test and Enhance Test Coverage

[mohiuddin-khan-shiam]

Changes

• Fixed the previously skipped test_solver_order_and_type in test_scheduler_edm_dpmsolver_multistep.py
• Properly separated testing of dpmsolver++ and sde-dpmsolver++ algorithms
• Added comprehensive validation for all supported solver orders and types
• Included output shape verification in test assertions
• Improved error messages for better debugging

Testing

• Verified all tests pass for both algorithm types
• Confirmed proper handling of solver order constraints
• Validated output shapes match expected dimensions

Impact

• Improves test reliability for the EDM DPM Solver
• Enhances maintainability with better test organization
• Provides clearer feedback when tests fail

[yiyixuxu]

can you take a look here? @DN6 @sayakpaul