Feat import export variable list (#68)

* adding functions to import/export variables
* pickle, yaml, and elf file format
* adding example program
* added test to check for import/export
- single variable
- multiple variables
- all variables
- yaml, pickle, and elf file
*elf_file cannot be exported

---------

Co-authored-by: Edras Pacola <edras.pacola@microchip.com>

Author: edras

pyx2cscope/variable/variable_factory.py

@@ -9,7 +9,7 @@
 from dataclasses import asdict
 
 from mchplnet.lnet import LNet
-from pyx2cscope.parser.elf_parser import DummyParser
+from pyx2cscope.parser.elf_parser import DummyParser, VariableInfo
 from pyx2cscope.parser.generic_parser import GenericParser
 from pyx2cscope.variable.variable import (
     Variable,
@@ -188,7 +188,6 @@ def get_variable(self, name: str) -> Variable | None:
         """
         try:
             variable_info = self.parser.get_var_info(name)
-
             return self.get_variable_raw(variable_info)
         except Exception as e:
             logging.error(f"Error while getting variable '{name}' : {str(e)}")