Patch Python executable name for Windows free-threaded builds (#8310)
A temporary fix for https://github.com/astral-sh/uv/issues/8298 while we
wait for my slower upstream fix at
https://github.com/indygreg/python-build-standalone/pull/373
I think we'll want this machinery anyway to ensure that the various
executable names are available? Otherwise we need to special-case all
the `python` names in `uv run`?
We don't have unit test coverage of managed downloads, so I added an
[integration
test](https://github.com/astral-sh/uv/actions/runs/11394150653/job/31703956805?pr=8310)
similar to what we have for Linux.