Rename dataset and output folder in Prior template

[Rensvandeschoot]

This pull request makes the naming conventions for datasets and output folders more intuitive and consistent, specifically:

• Renames the generated dataset with prior knowledge to dataset_custom_priors.
• Renames the output folder for results from data with custom priors to sim_custom_priors.asreview.
• Renames the output folder for results from data without priors to sim_minimal_priors.asreview.

These changes improve the legend labels to describe the datasets more accurately. Instead of using "with" and "without" (which may be ambiguous), the labels now clearly distinguish between "custom" and "minimal" priors, better reflecting the actual scenario.

Below is an updated plot with the new legend labels, using "custom" and "minimal" for clearer distinction (note that the colors are solved in #66):

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