fix: usr: Avoid extra round trips for DS lookups when the parent delegation is alread...

DS queries could take two unnecessary extra round trips when the resolver sent them to the child zone instead of the parent. The child responds with NODATA, forcing a recovery path to rediscover the parent delegation even though it was already cached.  The resolver now consults its delegation cache before starting DS fetches, sending queries directly to the correct parent nameservers and eliminating the extra latency.

Merge branch 'ondrej/fix-ds-chase' into 'main'

See merge request isc-projects/bind9!11835