more efficient array builder

[lmatz]

eliminate dynamic dispatch as much as possible

and maybe bulk append the rows so that static dispatch and dynamic dispatch (if not possible to remove all of them) are amortized. This does not necessarily contradict the per-row handling logic in the join operator.

checkout context: https://risingwave-labs.slack.com/archives/C034TRPKN1F/p1733464753437989

related: #20017 observe in the same experiment