Migrate direct transfer groups importer to Vue 3

What does this MR do and why?

Updates the Direct Transfer importer (Group imports) and related pages in Vue 3 compat using feature flag vue3_migrate_import_direct_transfer.

Key URLs:

• import/bulk_imports/status (after connecting to a source instance)
• import/bulk_imports/history (same as above)
• import/bulk_imports/failures (the import failed)
• groups/<group-name>/-/import_history
  • NOTE: page under development for future initiative. Hidden behind FF group_import_history_visibility)

Related entrypoints

• pages/import/bulk_imports/status/index.js
• pages/import/bulk_imports/history/index.js
• pages/import/bulk_imports/failures/index.js
• pages/groups/import_histories/show/index.js

References

#613597

Screenshots or screen recordings

URL	Before and After (unchanged)
import/bulk_imports/status
import/bulk_imports/history
import/bulk_imports/failures
groups/twitter/-/import_history (requires FF)

How to set up and validate locally

1. Turn on FFs. 2nd one is not required, as no real Vue components built yet for this feature

   Feature.enable(:vue3_migrate_import_direct_transfer)
   Feature.enable(:group_import_history_visibility) 

2. Enable direct transfer in admin settings http://127.0.0.1:3000/admin/application_settings/general#js-import-export-settings

3. Try a direct transfer migration (import one of your groups as a subgroup of an existing group).

   1. Go to groups/new#import-group-pane . You need your personal access token for this instance. Source URL is your current root such as http://127.0.0.1:3000/
   2. Verify you can import a group

MR acceptance checklist

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Related to #613597