Allow aliasing specific version to generic channels

[esemeniuc]

Problem you are trying to solve

I'm trying to install nightly-2024-10-25 as nightly, or 1.79.0 as stable to keep scripts as CI unchanged

Solution you'd like

rustup install nightly-2024-10-25 --default

Notes

No response

[djc]

I think most users would manage a rust-toolchain.toml file in their repo/workspace/project for this. Why is that not a feasible option for you?