Create (e.g.) `python3.13t` executables in `uv venv` (#14764)
## Summary
CPython's `venv` module creates these, so we should too.
On non-Windows, we add `python3.13t`.
On Windows, we add `python3.13t.exe` and `pythonw3.13t.exe` (see:
https://github.com/python/cpython/blob/65d2c51c10425dcfacc0a13810d58c41240d7ff9/Lib/venv/__init__.py#L362).
Closes https://github.com/astral-sh/uv/issues/14760.
