feat: reduce manual intervention required to initialize `midenup`'s `miden` command

Currently, in order to access the `miden` command manual intervention is required to add the `miden` symlink to the user's `$PATH`.
This can be a bit of a pain point in situations where a more automated approach is desired, like in a GitHub Action, like here for example: https://github.com/0xMiden/compiler/pull/896/changes#r2886279430.

A potential solution would be to have `midenup init` save the `miden` symlink directly in the default `~/.cargo/bin` directory