Add PEP 723 support to uv run (#4656)
Closes #3096
## Summary
Enables `uv run foo.py` to execute PEP 723-compatible scripts.
For example, given:
```python
# /// script
# requires-python = ">=3.11"
# dependencies = [
# "requests<3",
# "rich",
# ]
# ///
import requests
from rich.pretty import pprint
resp = requests.get("https://peps.python.org/api/peps.json")
data = resp.json()
pprint([(k, v["title"]) for k, v in data.items()][:10])
```
