Fix: incorrect child vector size in duckdb list array import

[connortsui20]

Fixes #5597

Since list views can be stored out of order and because there can be nulls at the end of the vector, we have to calculate the length of the child vector by looking at all views in the vector.

Note that this does not take validity into account, as I have no idea if DuckDB allows for complete garbage in their list views if they are null. At least in Arrow, that is not allowed.

Also adds 3 regression tests.

[codecov]

Codecov Report

❌ Patch coverage is 97.19101% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.23%. Comparing base (c93b6a7) to head (896dc20).

Files with missing lines	Patch %	Lines
vortex-duckdb/src/convert/vector.rs	97.19%	5 Missing ⚠️

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[connortsui20]

decided to add specialization on the validity