UseSWIG: Detect module name from interface file (#10080)

If no SWIG_MODULE_NAME is specified explicitly and the .i file exists,
scan it for the module name declaration.
UseSWIG: Revise and format documentation

Also add some documentation of SWIG_MODULE_NAME.
Merge topic 'UseSWIG-guess_module_name' into next

2c96192f UseSWIG: Revise and format documentation
e147c5c5 UseSWIG: Detect module name from interface file (#10080)