Added unit tests requested by Quantum Motion

[mcjamieson]

Summary

Added comprehensive input validation tests for quantum measurement and time evolution operations.

Changes

operations.cpp

• Added 12 validation test sections covering measurement, projection, and PauliStrSum operations
• Tests verify proper error handling for invalid quantum registers, out-of-bounds qubits, duplicate targets, and zero targets

trotterisation.cpp

• Added complete test suite for unitary and imaginary time evolution operations
• Includes 8 validation sections testing invalid inputs (bad registers, non-Hermitian Hamiltonians, invalid Trotter parameters)
• Added 4 correctness test scenarios for imaginary time evolution: strong magnetic field, opposite magnetic field, ferromagnetic system, and antiferromagnetic system. Each verifies the algorithm converges to the expected lowest-energy configuration.

Test Results

• All 12 operations validation tests pass
• applyTrotterizedUnitaryTimeEvolution: 19 assertions
• applyTrotterizedImaginaryTimeEvolution: 262,153 assertions

[otbrown]

Thanks Maurice! I'll add reviewing this to my list.

[tom-quantummotion]

Thanks @mcjamieson!

[otbrown]

There is a PR to the PR which fixes conflicts arising from Vasco's concurrent changes to the time evolution API!