feat(7430) - Add support to spawn python REPL with uvx python or uvx python@<version>

[mikeleppane]

Summary

This PR adds support to spawn Python REPL with the following commands:

uvx python # or
uvx [email protected] # or
uvx [email protected]

Test Plan

I added a few snapshot tests to the crates/uv/tests/tool_run.rs.

CI passes

Manual Tests

cargo run -- tool run python                                                                                                                                  ░▒▓ 99% 󰁹
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.42s
     Running `target/debug/uv tool run python`
Python 3.12.1 (main, Jan  8 2024, 05:57:25) [Clang 17.0.6 ] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

cargo run -- tool run [email protected]                                                                                                                           ░▒▓ 99% 󰁹
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.21s
     Running `target/debug/uv tool run '[email protected]'`
Python 3.9.20 (main, Sep  9 2024, 22:13:21)
[Clang 18.1.8 ] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

cargo run -- tool run [email protected]                                                                                                                        ░▒▓ 99% 
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.24s
     Running `target/debug/uv tool run '[email protected]'`
Python 3.13.0rc2 (main, Sep  9 2024, 22:13:26) [Clang 18.1.8 ] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

cargo run -- tool run [email protected]                                                                                                                         ░▒▓ 99% 
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.41s
     Running `target/debug/uv tool run '[email protected]'`
Python 3.13.0b3 (main, Sep 12 2024, 19:13:56) [GCC 13.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

Remarks/Questions

• uvx python@latest does not work, and I'm unsure how to handle this. Is this a valid alternative?
• uvx python launches REPL from system env? Is that correct? Or should it take the default interpreter from the virtual environment?
• uv tool run has many options when running uvx python. E.g. --python?
• Do you think we should document this change somewhere? If so, what would be the correct place?

Related to issue #7430