Refactor import_entities/import_groups app to use new pagination_bar

What does this MR do and why?

Related to #341868 (closed)

This MR prepares pagination_bar component for general use by putting it in vue_shared:

How to set up and validate locally

1. Open "New group" (/groups/new#import-group-pane)
2. Use https://gitlab.com as source instance and GeK1Nis4j-SY1X4sqE5c as personal access token (this token is from separate user on GitLab instance with 0 real data available, so we do not expose any security risks here)
3. Ensure pagination is displayed and working
4. Initiate some imports (no need for them to complete)
5. Go again to /groups/new#import-group-pane
6. Click "History"
7. Observe working pagination there
8. Run yarn storybook
9. Observe pagination_bar story

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.