[9.18] chg: dev: Process also the ISC_R_CANCELED result code in rpz_rewrite()

Log canceled resolver queries (e.g. when shutting down a hung
fetch) in DEBUG3 level instead of DEBUG1 which is used for the
"unrecognized" result codes.

Closes #4797

Backport of MR !9148

Merge branch 'backport-4797-rpz_rewrite-add-ISC_R_CANCELED-processing-9.18' into 'bind-9.18'

See merge request isc-projects/bind9!9348