chg: usr: Batch qp transaction for RPZ updates

RPZ was built around fine-grained locking, but that forces the use of many small qp transactions. With this MR, we switch qp transaction to handle the
full update to the rpz summary structure.
While this serializes the RPZ updates, the reduced overhead from batching qp transactions more than compensates for it and results in improvements for big RPZ zones.

Closes #5787, #6270

Merge branch '5787-batch-rpz' into 'main'

See merge request isc-projects/bind9!12411