SWIG 4.3.0 compatibility fixes

Description

• Small change in XML format output by SWIG and processed by generate_swig_iface.py
• Refactor internal SWIGLAL_MAYBE_RETURN_INT typemap
• Minor changes to lal/swig/SWIGTestLALPython.py

API Changes and Justification

Backwards Compatible Changes

• This change does not modify any class/function/struct/type definitions in a public C header file or any Python class/function definitions
• This change adds new classes/functions/structs/types to a public C header file or Python module

Backwards Incompatible Changes

• This change modifies an existing class/function/struct/type definition in a public C header file or Python module
• This change removes an existing class/function/struct/type from a public C header file or Python module

Review Status

N/A