chg: dev: Remove nodep from the dns_db_find() API

Previously `dns_db_find()` return four values: a result, an rdataset, the name of the rdataset and a pointer to the node containing the rdataset (`nodep`). With a few tweaks the node pointer can be made superflous, as the node can be retrieved from the rdataset name using `dns_db_findnode()`.

This MR removes the `nodep` output parameter from `dns_db_find()`, leading both an API simplification and speedups when serving NSEC signed zones.

Merge branch 'alessio/no-qctx-node-v2' into 'main'

See merge request isc-projects/bind9!12458