fix: usr: Fix TCP fallback after repeated UDP timeouts

When an authoritative server failed to respond to two consecutive
UDP queries in a fetch, named was supposed to retry the next attempt
over TCP but in fact still sent it over UDP.  The resolver now
properly switches the transport to TCP on the third attempt to
the same server.

Closes #5529

Merge branch '5529-fix-tcp-fallback-after-udp-timeouts' into 'main'

See merge request isc-projects/bind9!12022