feat (closes #7246): add new component: leafcutter/differentialsplicing

[JTL-lab]

PR Description

This PR adds a new module leafcutter/differentialsplicing for running Leafcutter differential splicing analysis to determine statistically significant junction usage changes between biological conditions of interest. This module relies on the new Python reimplementation of Leafcutter (leafcutter-ds) here (also documented in the meta.yml).

PR checklist

Closes #7246

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