add comand for uninstalling all toolchains

[e00E]

Problem you are trying to solve

I have many toolchains installed as seen by rustup toolchain list. I want to uninstall all of them. This is tedious to do by hand. Also, if you want to do this in an automated fashion, you need to parse rustups output to know which toolchains to uninstall.

Solution you'd like

A command like rustup toolchain uninstall-all that uninstalls all toolchains.

Notes

No response

[rami3l]

Duplicate of #2530.