Convert filter to Attributes for Drupal 11+

Problem/Motivation

Attribute-based plugin discovery was enabled in Drupal 10.3, while D8 traditional reflection-based plugin discovery is going to be deprecated, so we need to follow the trend.

Proposed resolution

• Add an attribute-based plugin definition, keeping the reflection version
• Publish a release with that double compatibility once Drupal 11.0.0 is released
• Later, once Drupal 10.2 is EOL, presumably in 2025, remove the reflection version in a followup.

Remaining tasks

• Implement attribute-based discovery
• Qualify it with a test

User interface changes

None.

API changes

None.

Data model changes

Attribute-based discovery becomes available.