[FEATURE] Implement a `.merge` method for `QasmModule`

[TheGupta2012]

Feature Description

Implement a.merge() method with automatic unrolling and register consolidation.

• Purpose:
  Merge two QasmModule objects into a single module, handling all register consolidation and unrolling transparently.
• Consolidation & Unrolling:
  • All register consolidation and unrolling is performed automatically during the merge.
  • Uses the existing .unroll(device_qubits) method to ensure both modules are unrolled and consolidated before merging.
• User Experience:
  • The user only needs to call .merge() on one module, passing the other as an argument.
  • No manual unrolling or consolidation is required.
• Output:
  • Returns a new, merged module (preferred for immutability).
  • All qubit and classical registers are consolidated into __PYQASM_QUBITS__ and __PYQASM_CLASSICAL__.

Implementation (Optional)

1. Unroll and Consolidate Both Modules:
   • Call .unroll(device_qubits=...) on both modules before merging.
   • If device_qubits is not specified, use a default large enough to hold all qubits.
   • This ensures all registers are consolidated and unrolled.
2. Merge Gates and Operation History:
   • Append gates from the second module after the first.
   • Combine operation history lists.
3. Consolidate the Merged Module (Optional, but Safe):
   • If the merge could introduce new registers (unlikely if both are already consolidated), perform a final consolidation.
   • This step is mostly redundant but ensures robustness.
4. Return the New Module:
   • Return a new QasmModule with the merged content.