feat: add partial toolchain support from CLI

[lima-limon-inc]

Currently, installing partial toolchains is limited to the miden-toolchain.toml file for a specific directory.

This functionality could be re-surfaced in other areas of midenup.

@plafer suggested that the installation process could be interactive (i.e. prompts for verification before installing each component).

I believe the feature would mean an improvement in UX, however, maybe it could be limited to cases where miden auto installs toolchains instead of always prompting for confirmation; keeping midenup install stable the same.