chg: dev: Incrementally apply AXFR transfer

Reintroduce logic to apply diffs when the number of pending tuples is
above 128. The previous strategy of accumulating all the tuples and
pushing them at the end leads to excessive memory consumption during
transfer.

This effectively reverts half of e3892805d6

Closes #4986

Merge branch '4986-axfr-chunked-insert' into 'main'

See merge request isc-projects/bind9!9740