fix: usr: Fix dig -x crash on excessively long arguments

dig -x crashed with a segmentation fault rather than printing an
error when given an argument with thousands of dot-separated
components. dig -x now rejects such inputs cleanly with "Invalid IP
address".

Closes #5917

Merge branch '5917-dig-reverse-octets-stack-overflow' into 'main'

See merge request isc-projects/bind9!11928