Add more tests for array support

#969 introduced some support for C++ arrays. So far, we know this works for fields of structs. We should add more tests to find out what happens if we allow arrays as actual function parameters, etc. Pretty sure it won't work because the support for arrays in `TypeConverter` is incomplete. But, we should find out!

Start by reviewing issue #969 and the incomplete array handling in `TypeConverter`, then inspect the existing tests for arrays used as struct fields. Add tests covering arrays as function parameters and other relevant uses, and use the results to establish which cases currently work and which remain unsupported.

Written by the indexing model from the issue text.