Auto merge of #5041 - pwoolcoc:display-path-to-custom-commands-when-verbose, r=matklad

When -v is passed with --list, display path to custom commands

With this change, output of `cargo --list` changes slightly when 1 or more `-v` flags are passed:

```
 ± ./target/debug/cargo --list -v
Installed Commands:
    add                  /path/to/home/.cargo/bin/cargo-add
    bench
    build
    canoe                /path/to/home/.cargo/bin/cargo-canoe
    check
    clean
    do                   /path/to/home/.cargo/bin/cargo-do
    doc
    fetch
    fmt                  /path/to/home/.cargo/bin/cargo-fmt
    ...
```