Add dataset /presidio-entities endpoint (#2846)
* add dataset-presidio-entities-count
* add to graph
* fix tests for graph
* add /presidio-entities endpoint
* child of dataset-split-names
* add openapi
* fix tests
* fix openapi
* Apply suggestions from code review
Co-authored-by: Sylvain Lesage <sylvain.lesage@huggingface.co>
---------
Co-authored-by: Sylvain Lesage <sylvain.lesage@huggingface.co>
