Refactor import logic in ai_dashboard

[valthebald]

With module issues gradually moving to gitlab, there is a need to import issues from 2 sources: drupal.org and gitlab.
The current logic in ai_dashboard contains slabs for gitlab import, but the rest of the code is heavily leaned towards d.o. import, from the structure of API responses to the field mapping in database.

Also, there is a dependency loop in ImportService <=> BatchImportService.

I think there is a need in refactoring the whole importing logic.

Will start with providing a plan

[valthebald]

here's the plan https://github.com/WiseTrout/Drupal-AI-Dev-Tracker/blob/gitlab-refactoring/refactoring-plan.md

[nickopris]

We can simplify by running everything in batches, no matter of volume.