Switch to Dex / Common CLI entrypoint

Problem/Motivation

Move all the custom entry point stuff with `sm` to use `dex` instead.

This is considered a break, and will result in a new minor 0.x minor.

Any executors must switch from bin/sm to bin/dex.

https://www.drupal.org/project/dex_console → will be added as a dependency.

Note: Dex' functionality disables itself if it detects the site is using the core https://www.drupal.org/project/drupal/issues/3453474 ✨ CLI entry point in Drupal Core (Dex) Needs review patch instead.