[Meta] Tasks to remove both Aggregator and our dependency on Laminas Feed

Problem/Motivation

In #1136482: [policy] Deprecate aggregator.module in D9 core and remove it in D10 we've agreed to deprecate the Aggregator module for removal in Drupal 10, along with Laminas Feed (which only Aggregator depends on).

This issue is to coordinate and track the steps needed to remove Aggregator after it is deprecated. See Remove a core module and move it to a contributed project of the deprecation policy.

Proposed resolution

Remaining tasks

1. Manually test upgrading from the core module to the contrib module. #3303420: Manually test aggregator module removal
2. Move all core documentation for Aggregator module to the contrib project.

TBD

API changes

TBD

Data model changes

TBD

Release notes snippet

TBD

Done

1. Remove Aggregator module and Laminas from core
   • #3264120: Remove aggregator module and our dependency on Laminas Feed
2. Open an issue against https://www.drupal.org/project/project_composer. #3272246: Ensure that aggregator doesn't get special core treatment
3. Move core issues for Aggregator module from the core queue to the contrib module.
   • #3272651: Move core issues for Aggregator module from the core queue to the contrib module
   • When #3272246: Ensure that aggregator doesn't get special core treatment is Fixed update the documentation with the new composer command.

User interface changes