Migration dependency for comment status is not evaluated

Problem/Motivation

1. d7_disqus_comment_status contains a dependency which isn't evaluated by the Migrate API: d7_node:*. It should be only d7_node.
2. Most of the Disqus migrations are missing the migration tags (Configuration and Content).
3. The Drupal 9 disqus field value lacks schema

Steps to reproduce

Proposed resolution

Since the d7_disqus_comment_status migration only updates already migrated nodes (and only their most recent default revision), the right solution is that this migration should be replaced with a plugin alter (which adds the process pipeline for the disqus field) and with a prepare hook (which adds the appropriate status and identifier field values). This also means that, we should add a deriver class for the d7_disqus_field migration, and make all node migrations depend on the corresponding d7_disqus_field derivative.

Remaining tasks

User interface changes

API changes

Data model changes