Update Drush commands for Drush 12+

Problem/Motivation

Drush 11 is EOL. Drupal 10 requires Drush 12.5+.

Drush 12 works on Drupal 10 but not Drupal 11.
Drush 13 is required for Drupal 11 but will also work on Drupal 10.2+.

https://www.drush.org/13.x/install/#drupal-compatibility

Proposed resolution

Upgrade search_api Drush commands for Drush 12+.

The big things here are to use PHP Attributes instead of Annotations for Commands, and to use autodiscovery instead of drush.services.yml, and to use autowiring instead of service injection.

These things are supported by Drush 12 and required in Drush 13.

Remaining tasks

Basic steps that apply to this module are:

• Change namespace and class naming according to https://www.drush.org/12.x/commands/#auto-discovered-commands-psr4
• Add use statement for Drush PHP attribute classes.
• Use PHP attributes for Drush command definitions, as per https://www.drush.org/12.x/commands/#attributes-or-annotations
• Do not remove the Drush annotations yet - that will make these changes easier to review and easier to fix if a problem is noticed.
• Remove drush.services.yml and remove drush.services.yml from composer.json. Drush commands will be autoloaded.
• Use Autowire instead of dependency injection.
• Add parameter and return type hints to all methods. Turn on strict_types.