Introduce League Oauth into the module

Update Patreon Service to obtain API token as League entities, store them, retrieve them and refresh them if required before using.

Deprecates a number of methods in the PatreonService that are no longer required (or are difficult to maintain), and upgrades the codebase for use with PHP 8.3. Removes support for Drupal 9. See https://www.drupal.org/project/patreon/issues/3083491 for details.