improvements for creating and using offline mirror for uv-python

[MeitarR]

Summary

This is a follow-up for #10203 and #10939

The current flow to set up and use an offline Python mirror is described here

It can improve in some ways

• Support http/https URLs in uv python --python-downloads-json-url #14687
• Add python-downloads-json-url option for uv.toml to configure custom Python installations via JSON URL #12974
• improve the create-python-mirror script to output matching json (only the downloaded versions and maybe also modify the URL)

Example

No response