`ComplexCopier` missing support for FixedSizeBinary columns

[nbauernfeind]

Complex copier does not support fixed size binary.

java.lang.UnsupportedOperationException: FIXEDSIZEBINARY
	at org.apache.arrow.vector.complex.impl.ComplexCopier.getListWriterForReader(ComplexCopier.java:824)
	at org.apache.arrow.vector.complex.impl.ComplexCopier.writeValue(ComplexCopier.java:93)
	at org.apache.arrow.vector.complex.impl.ComplexCopier.copy(ComplexCopier.java:76)
	at org.apache.arrow.vector.complex.ListVector.copyFrom(ListVector.java:409)

[Maria-Berta]

Hi @lidavidm @nbauernfeind @axreldable! I'd like to work on this issue. I'm a CS graduate with hands-on Java experience and I've recently contributed to Apache phpMyAdmin through CodePath's AI301 course, so I'm familiar with the Apache contribution process.
From reading the stack trace, it looks like getListWriterForReader in ComplexCopier.java is missing a case for FIXEDSIZEBINARY — the fix would involve adding that case similar to how other types like VARBINARY are already handled. Could you confirm this approach is on the right track, and point me to any existing tests for ComplexCopier I should model new tests after?
Thanks!