LSDB.nested NestedFrame parquet I/O Serialization support

[dougbrn]

Feature request
LSDB.nested NestedFrame parquet I/O is currently not updated to be able to serialize nested columns on read or write, like nested-pandas and LSDB.catalog I/O both now can.

I think this is low priority, but we should update these at some point. See this closed PR for an 80% implementation: #727

This will just limit the ability for users to write more general parquet through the _ddf interface, for example:

# writing out
cat._ddf.to_parquet("catalog_as_normal_df.parquet")

# reading in
from lsdb.nested import read_parquet
ndf = read_parquet("catalog_as_normal_df.parquet")

My assumption is that the above is not really that important to have right now, and I could even see an argument being made to limit this ability all together.

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