Optimize executable discovery and fix MATLAB versioning

[samarkanov]

This PR refactors the executable discovery logic to support custom paths, see the issue #415

Changes:

• Introduced can_handle(path, script_file) class method to the Executable base class to allow identifying the correct subclass before instantiation.
• Refactored get_executable() to use a discovery-first approach: iterate through registered types and call can_handle() to find the most specific subclass
• Updated MatlabExecutable._get_version() to use self.path.
• Fixed RExecutable.executable_names to be a consistent tuple ('Rscript',)
• Added os.remove("test_file.yml") to the tearDown() method in test/unittests/test_parameters.py