Python native callbacks with 2+ parameters fail with 'binding parameter a second time' in 0.22.0

## Summary
In jsonnet 0.22.0, Python native callbacks registered with two or more parameters fail at runtime if all parameter names have a length of 2 or more characters. The error is:

```
RUNTIME ERROR: binding parameter a second time:
```

This appears to be a regression introduced in 0.22.0 (likely related to PR #1299 which changed built-in function argument binding).

## Environment
- jsonnet version: 0.22.0
- Python version: 3.13.13 (also reproduced on 3.10+)
- OS: Linux

## Minimal Reproduction

```python
import _jsonnet

def my_func(a, b):
return "{} {}".format(a, b)

# This FAILS in 0.22.0 (worked in 0.21.0)
result = _jsonnet.evaluate_snippet(
"test",
'std.native("my_func")("a", "b")',
native_callbacks={"my_func": (("target", "path"), my_func)}
)
```

Error:
```
RuntimeError: RUNTIME ERROR: binding parameter a second time: path
```

## Observations

1. **Single-parameter callbacks work fine** regardless of name length.
2. **At least one parameter must be 1 character long** for multi-param callbacks to work:
```python
# WORKS (one 1-char param)
(("t", "path"), my_func)
```
3. **The issue affects all multi-param native callbacks**, not just specific names.
4. **This broke existing code** — Kapitan (https://github.com/kapicorp/kapitan) had to shorten parameter names as a workaround: https://github.com/kapicorp/kapitan/pull/1496

## Expected Behavior
Native callbacks with multi-character parameter names should work as they did in 0.21.0.

## Actual Behavior
Runtime error when evaluating any native callback where all parameter names are ≥2 characters.

## Regression Range
- 0.21.0: Works
- 0.22.0: Broken

## Related
- PR #1299 — "Fix some behaviour of builtin functions"