Issue #965 npf from imod5

[luitjansl]

Fixes #965

Description

Adds a function to import an npf package from an imod5 project file. Adds tests.

Checklist

• [x] Links to correct issue
• [ ] Update changelog, if changes affect users
• [x] PR title starts with Issue #nr, e.g. Issue #737
• [x] Unit tests were added
• [ ] If feature added: Added/extended example