Implement missing types

[chmp]

• Sparse union arrays
• Interval arrays
  • the arrays are using types without bytemuck support. How can they be safely cast into a common repr (in particular for views)? For arrow the crate offers a view as a &[u8] which could be (safely) transmuted
  • Before "arrow=52" the Interval types are broken (issue). The bits generated by marrow are still correct, but the tests will fail
  • Figure out whether the alignment is an issue. See here
    • the structured types are aligned to their largest member (4 bytes for DayTime, 8 bytes for MonthDayNano)
• Run end encoding arrays
• Document
  • Include note about the Interval impl before arrow=52