chg: dev: Remove unused foundname parameter

The `foundname` parameter in `qp.c:dns_qp_lookup` was effectively used only in unit tests, as in every case the name is needed, it can be retrieved directly from the node pointer. It also required an inefficient implementation that extracted the name by converting it into a key and then immediately converting it back.

This MR refactors `qp.c:dns_qp_lookup` not to have a foundname parameter, resulting in a 5% speedup in the handling of NXDOMAIN responses in perflab.

Merge branch 'alessio/qp-no-foundname' into 'main'

See merge request isc-projects/bind9!11339