Automatically retry on create_repo if '409 conflicting op in progress'

[Wauplin]

Since moon-landing#7272 (private repo), it is not possible to concurrently create repos on the Hub for a same user. This is rarely an issue, except when running tests (it is actually breaking all CI tests at the moment 😕). This PR makes the lib' retry until the repo is created or a "real" error occurs.

Notes:

• Most users should not be impacted by this change. Worst case scenario, it's still better than having a 409 and retry manually. Infinite loops shouldn't be a problem (:crossed_fingers:)
• This could have being fixed directly in the tests but adding it here should fixed CIs for all dependent libraries.
• If a fix is implemented server-side, we should be able to remove this retry mechanism.

cc @SBrandeis @Kakulukian @allendorf

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.

[LysandreJik]

Approved offline with @Wauplin