Check in test script for uv run <url> (#7708)
Merge before #6375 (see
https://github.com/astral-sh/uv/pull/6375#discussion_r1776975298)
This is testing a couple of things at once, and I'm happy to strip back
to something more simple (i.e., "just" printing).
However, I figured it would be useful to ensure that the PEP 723
metadata correctly works as well as that
additional arguments are correctly forwarded to the Python program.
cc: @burntsushi
