chore: make .igraph.progress() and .igraph.status() more internal

[maelle]

last item for #685

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[aviator-app]

This pull request failed to merge: some required checks failed. After you have resolved the problem, you should remove the blocked pull request label from this PR and then try to re-queue the PR. Note that the pull request will be automatically re-queued if it has the mergequeue label.

Failed checks: Check ubuntu-20.04 (release), Check ubuntu-20.04 (oldrel-4)

[aviator-app]

This pull request failed to merge: some required checks failed. After you have resolved the problem, you should remove the blocked pull request label from this PR and then try to re-queue the PR. Note that the pull request will be automatically re-queued if it has the mergequeue label.

Failed checks: Check ubuntu-20.04 (release), Check ubuntu-20.04 (oldrel-4), Check ubuntu-20.04 (oldrel-3)