Show skipped MRs in project import statistics
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This is the front-end MR for https://gitlab.com/gitlab-org/gitlab/-/issues/537939.
Once the skipped MR data is available via the API, we should show it in the front-end for the project import statistics.
Sample designs ([source](https://gitlab.com/gitlab-org/gitlab/-/issues/463562#note_2407957450)):
| current view | import_history_table |
| ------ | ------ |
|  |  |
The text should be "Excluded for lack of diffs"[^text]
[^text]: https://gitlab.com/gitlab-org/gitlab/-/issues/463562#note_2449430962
#### Docs
Update the docs about the skipped items and why they are skipped.
issue