Check node being available on filtered queryset to prevent index error.

[rtibbles]

Summary

• Due to a difference in the queryset filtering for existence checking and the queryset returned from the get_tree_queryset method, it was possible for entirely filtered nodes to not return a 404 from the content node tree endpoint
• This adds a regression test for this by filtering a specific node and adding a filter parameter that no node can pass (a non-existent but valid parent id)
• This fixes this issue by filtering the queryset used for the existence check in the same way as the returned queryset

References

Fixes #9537

Reviewer guidance

Make a request to /api/content/contentnode_tree/<existing_id>/?parent=<valid_but_nonexistent_id> and confirm that it does not produce a 500.

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Reviewer checklist

• Automated test coverage is satisfactory
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[marcellamaki]

LGTM - does fix the issue described from being a 500 error to now be a 404