Explore automatic document score threshold generation for HPLT

[eu9ene]

The statistics about the document score are available here as yaml: https://github.com/hplt-project/data-analytics-tool/tree/main/reports/mono-2.0

We could do things with it. For example, validating that the default scores cover at least 10% of the data or taking some percentile and using the corresponding score in the config generator.