[CS 598] Add vaso/vent dataset configs and tasks for MIMIC-III/IV

[damphessian]

Changes

• Adds YAML configuration files for derived datasets for vasopressor and ventilation durations for MIMIC-III and MIMIC-IV.
• Adds associated vaso / vent duration tasks drawn from "Racial Disparities and Mistrust in End-of-Life Care" (Boag et al., 2018)

Files Added

• pyhealth/datasets/configs/mimic3_derived.yaml
• pyhealth/datasets/configs/mimic4_derived.yaml
• pyhealth/tasks/mimic_derived_interventions.py
• tests/core/test_mimic_derived_interventions.py

Files modified

• pyhealth/tasks/__init__.py