2.1.0: WP-CLI commands

WP-CLI commands to set up and run the plugin without wp-admin (wp help mpcl).
No command prints the API token or key material.

• wp mpcl connect --key=<key> [--sync] saves the API credentials; the token is
  read from STDIN and checked before saving. wp mpcl disconnect [--purge]
  removes them, and with --purge the synchronised machines.
• wp mpcl test-connection checks the saved credentials and exits non-zero on
  failure, for use in monitoring.
• wp mpcl sync [--reset] synchronises right away and reports the number of
  machines or the reason of a failure.
• wp mpcl schedule enable [--interval=1h]|disable|status controls the
  automatic synchronisation.
• wp mpcl status shows the connection, synchronisation and catalogue state
  without calling the API.
• wp mpcl config list|get|set reads and changes the settings with the same
  validation as the settings page.
• wp mpcl catalog create-page|set-page creates or chooses the catalogue page.
• wp mpcl machines list|get shows the synchronised machines.
• wp mpcl secrets status|generate-key [--write]|rekey manage the encryption
  key: add or remove MPCL_ENCRYPTION_KEY without re-entering the API token,
  and recover the token after the salts were shuffled (old salt read from STDIN).
• Declares compliance with the WP Consent API, so Site Health no longer lists
  the plugin as not compliant. The plugin sets no cookies.
• The plugin's author is now Reprostar, and its address points to the
  lowercase GitHub organisation (github.com/reprostar/mpcl-wordpress).
• A token encrypted with the salt still reads after MPCL_ENCRYPTION_KEY is
  added. Saving the settings no longer re-encrypts an unchanged token, and keeps
  a token that cannot be decrypted so that it can still be recovered.

Requires WordPress 6.9+ and PHP 7.4+. Updating from 2.0.x needs no extra steps.