uv

0593b967 - Add `python-downloads-json-url` option for `uv.toml` to configure custom Python installations via JSON URL (#12974)

Add `python-downloads-json-url` option for `uv.toml` to configure custom Python installations via JSON URL (#12974) ## Summary Part of #12838. Allow users to configure `python-downloads-json-url` in `uv.toml` and not just from env. I followed similar PR #8695, so same as there it's also available in the CLI (I think maybe it's better not to be configurable from the CLI, but since the mirror parameters are, I think it's better to do the same) ## Test Plan <!-- How was it tested? -->