fix: dev: Refactor resolver cache_name() and validated() functions

These functions were excessive in length and complexity, with McCabe complexity values of 110 and 105 respectively, and also included some dead code. They have been cleaned up and split into smaller functions, with a maximum complexity of 27.  A few minor coding errors were discovered and fixed along the way.

Merge branch 'each-refactor-cache-name' into 'main'

See merge request isc-projects/bind9!10198