Allow importing parquet fields containing repeated elements.

[nicktobey]

NOTE: This still needs tests. I'm looking for a good tool for generating parquet. We can't use dolt table export to generate the parquet because we can't generate composite types that way.

This PR adds support for importing specific composite parquet types into Dolt. Specifically, we're now able to import a compose parquet field if:

• There is exactly one leaf column in the field.
• There is at most one repeated tag in the field.

We flatten these composite values into a single primitive value (if there are no repeated tags) or an array of primitive values (if there's exactly one repeated tag.)

There's more work to be done here (multidimensional arrays, objects, etc), but this allows us to import vector embedding stored in parquet files.

Why do we flatten the type?

We want to be able to import parquet files from HuggingFace, and store embedding sequences as arrays. Embedding sequences in HuggingFace exports are an optional field containing a single repeated child field, which itself contains a single optional field containing the sequence element. Flattening this into a single array is more usable and doesn't lose any data.

[coffeegoddd]

@nicktobey DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
75dd73f	ok	5937457

version	total_tests
75dd73f	5937457

correctness_percentage
100.0

[coffeegoddd]

@coffeegoddd DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
d1eba8f	ok	5937457

version	total_tests
d1eba8f	5937457

correctness_percentage
100.0

[jennifersp]

LGTM!

[coffeegoddd]

@nicktobey DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
63eddeb	ok	5937457

version	total_tests
63eddeb	5937457

correctness_percentage
100.0

[coffeegoddd]

@coffeegoddd DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
09d42a4	ok	5937457

version	total_tests
09d42a4	5937457

correctness_percentage
100.0