[378906] Github import: rate limit handling on import list fetch

What does this MR do and why?

A fix for Github api rate limit not handled correctly when importing project with single_endpoint_notes_import option set to true

Screenshots or screen recordings

How to set up and validate locally

Import a big/huge repository from GitHub to GitLab through an API (as most likely you don't have straight access to such a huge repos there, but if you do - feel free to use UI) with single_endpoint_notes_import optional stage. In this particular case we tested it on rspec/rspec-core.

API request body example

{
    "personal_access_token":"<your PAT>",
    "repo_id":238972,
    "target_namespace":"root",
    "new_name":"rspec-core-single-endpoint2",
    "optional_stages": {"single_endpoint_issue_events_import":false,"single_endpoint_notes_import":true,"attachments_import":false}
}

MR acceptance checklist

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

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