Implement lists::concatenate_list_elements

[ttnghia]

This PR implements lists::concatenate_list_elements for list type. Given a lists column in which each row is a list of lists, the output column is generated by concatenating all lists in the same row into a single list.

Example:

l = [ [{1, 2}, {3, 4}, {5}], [{6}, {}, {7, 8, 9}] ]
r = lists::concatenate_list_elements(l);
r is [ {1, 2, 3, 4, 5}, {6, 7, 8, 9} ]

This closes #8164. In addition, lists::concatenate_rows is rewritten using lists::interleave_columns following by lists::concatenate_list_elements, which is significantly shorter.

[ttnghia]

Reference: #8006

[codecov]

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[robertmaynard]

Approving CMake changes.

[jlowe]

Java approval

[ajschmidt8]

Approving ops-codeowner file changes

[devavret]

This code is giving me major déjà vu. Can you try to consolidate this with lists::concatinate_rows? There seems to be lot of shared logic. Even better, it looks like the entirety of lists::concatinate_rows can be reimplemented as an interleave_columns followed by a concatenate_list_elements.

[galipremsagar]

This file would likely have to be renamed too to combine.pxd

[ttnghia]

Thanks. Done.

[devavret]

This much better

[ttnghia]

Rerun tests.

[ttnghia]

@gpucibot merge