[BE] Prefer dash over underscore in command-line options (#94505)

Preferring dash over underscore in command-line options. Add `--command-arg-name` to the argument parser. The old arguments with underscores `--command_arg_name` are kept for backward compatibility.

Both dashes and underscores are used in the PyTorch codebase. Some argument parsers only have dashes or only have underscores in arguments. For example, the `torchrun` utility for distributed training only accepts underscore arguments (e.g., `--master_port`). The dashes are more common in other command-line tools. And it looks to be the default choice in the Python standard library:

`argparse.BooleanOptionalAction`: 4a9dff0e5a/Lib/argparse.py (L893-L895)

```python
class BooleanOptionalAction(Action):
    def __init__(...):
            if option_string.startswith('--'):
                option_string = '--no-' + option_string[2:]
                _option_strings.append(option_string)
```

It adds `--no-argname`, not `--no_argname`. Also typing `_` need to press the shift or the caps-lock key than `-`.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/94505
Approved by: https://github.com/ezyang, https://github.com/seemethere

test/test_jit_fuser.py

@@ -75,7 +75,7 @@ class TestFuser(JitTestCase):
             shell_env = os.environ.copy()
             shell_env['TMP'] = dname
             cmd = [sys.executable, os.path.basename(__file__), type(self).__name__ + '.test_abs_cpu']
-            legacy_jit_flag = '--jit_executor=legacy'
+            legacy_jit_flag = '--jit-executor=legacy'
             for v in sys.argv:
                 if v == legacy_jit_flag:
                     cmd.append(legacy_jit_flag)