Use PHP attributes instead of annotations

Problem/Motivation

Since Drupal 10.2, core uses PHP attributes instead of annotations.
Follow this pattern by converting the existing plugin annotations to attributes.

Proposed resolution

See https://www.drupal.org/docs/drupal-apis/plugin-api/attribute-based-plugins →

Remaining tasks

- Convert plugin annotations to attributes.
- Update the supported Drupal core version to 10.2+

User interface changes

N/A

API changes

N/A

Data model changes

N/A