Description of problem:

Improve or add new API endpoints to use the REX functionality instead of katello-agent

Version-Release number of selected component (if applicable):
satellite-6.10

How reproducible:
When using /api/hosts/:host_id/packages/

Steps to Reproduce:
1. Modify setting remote_execution_by_default | true
2. Use the "Curl" command to install package/errata
3. This process use katello-agent

Actual results:

PUT /api/hosts/:host_id/errata/apply DEPRECATED Schedule errata for installation using katello-agent. NOTE: Katello-agent is deprecated and will be removed in a future release. Consider using remote execution instead.

PUT /api/hosts/:host_id/packages/install DEPRECATED Install packages remotely using katello-agent. NOTE: Katello-agent is deprecated and will be removed in a future release. Consider using remote execution instead.

PUT /api/hosts/:host_id/packages/upgrade DEPRECATED Update packages remotely using katello-agent. NOTE: Katello-agent is deprecated and will be removed in a future release. Consider using remote execution instead.

PUT /api/hosts/:host_id/packages/upgrade_all DEPRECATED Update packages remotely using katello-agent. NOTE: Katello-agent is deprecated and will be removed in a future release. Consider using remote execution instead.

PUT /api/hosts/:host_id/packages/remove DEPRECATED Uninstall packages remotely using katello-agent. NOTE: Katello-agent is deprecated and will be removed in a future release. Consider using remote execution instead.

PUT /api/hosts/bulk/install_content DEPRECATED Install content on one or more hosts using katello-agent. NOTE: Katello-agent is deprecated and will be removed in a future release. Consider using remote execution instead.

PUT /api/hosts/bulk/update_content DEPRECATED Update content on one or more hosts using katello-agent. NOTE: Katello-agent is deprecated and will be removed in a future release. Consider using remote execution instead.

PUT /api/hosts/bulk/remove_content DEPRECATED Remove content on one or more hosts using katello-agent. NOTE: Katello-agent is deprecated and will be removed in a future release. Consider using remote execution instead.

Expected results:
either keep those Endpoints and migrate them to REX or introduce new Endpoints for REX like "/api/v2/katello/remote_execution".

Additional info: