Change in `mkdir` `-s` flag to `-v` to be similar to other commands
# Description
Other commands like `rm`, `mv`, `cp` have a `-v` (`--verbose`) flag.
`mkdir` has a `-s` (`--show-created-paths`), but should be consistent
with other commands.
# User-Facing Changes
- flag `-s` replaced by `-v` in `mkdir` command.
# Tests + Formatting
```
> mkdir -v new_dir
╭───┬───────────────────────────────────╮
│ 0 │ C:\Users\ricardo.monteiro\new_dir │
╰───┴───────────────────────────────────╯
```
* update docs to refer to length instead of count
* rename count to length
* change all occurrences of 'count' to 'length' in tests
* format length command
* move commands, futures.rs, script.rs, utils
* move over maybe_print_errors
* add nu_command crate references to nu_cli
* in commands.rs open up to pub mod from pub(crate)
* nu-cli, nu-command, and nu tests are now passing
* cargo fmt
* clean up nu-cli/src/prelude.rs
* code cleanup
* for some reason lex.rs was not formatted, may be causing my error
* remove mod completion from lib.rs which was not being used along with quickcheck macros
* add in allow unused imports
* comment out one failing external test; comment out one failing internal test
* revert commenting out failing tests; something else might be going on; someone with a windows machine should check and see what is going on with these failing windows tests
* Update Cargo.toml
Extend the optional features to nu-command
Co-authored-by: Jonathan Turner <jonathandturner@users.noreply.github.com>
