Add Parquet reader support for Variant

[the-other-tim-brown]

Task Description

What needs to be done:
Add parquet reader support for Variant so that files with this data type can be read back into Hoodie Records or engine specific row types.

Update functional tests in spark to ensure that the data can be read back properly.

Why this task is needed:
After this is completed along with the writer support, we should be able to have a simple CoW workflow with variant data.

Task Type

Code improvement/refactoring

Related Issues

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