Add Container Expiration Policy & Service Desk Setting to GitLab Migration

What does this MR do and why?

Related to #339416 (closed)

⚠ this feature is behind bulk_import_projects feature flag that is currently off by default (and disabled on .com).

This MR adds Container Expiration Policy & Service Desk Setting migration when using Group Migration that includes projects (https://docs.gitlab.com/ee/user/group/import/). Similar to other MRs from this series.

Screenshots or screen recordings

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How to set up and validate locally

1. Feature.enable(:bulk_import).
2. Feature.enable(:bulk_import_projects).
3. Create a top level group and project in it.
4. Create project service desk setting as well as container expiration policy
5. Go to /groups/new#import-group-pane page and enter instance url and access token (needs to be api & read_repository scope).
6. Select newly created group and click Import.
7. Wait for Group import to complete and verify imported settings. They should be present and their values should be preserved.

MR acceptance checklist

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