Add alternate manylinux targets to `--python-platform` (#3229)
## Summary
I initially implemented this by allowing arbitrary
`x86_64-manylinux_x_y`, but it makes the Clap, Serde, and Schemars
definitions more complicated, _and_ makes it harder for the user.
Ultimately, manylinux itself only provides images for 2_17 and 2_28, so
this seems like it should be sufficient.
Closes https://github.com/astral-sh/uv/issues/3222.
