pdl: Generate additional canonical test vectors

- Add tests with min and max scalar values
- Add tests for array with a size field and
  dynamically sized elements
  (real life example TLV buffers)
- Fix python generation bug with said arrays

Test: atest --host pdl_python_generator_test
Change-Id: Iad255cc452399967e24e212a82aff747fca3b37e