new: usr: Provide response round-trip time (RTT) counters via statistics channel

Previously, :iscman:`named` provided RTT counters for outgoing
queries performed by itself during name resolutions. Now this
has been improved to provide more granular counters (histogram),
and to also provide RTT counters for the incoming queries.

Closes #5279

Merge branch '5279-query-rtt-isc_histo_t-statistics' into 'main'

See merge request isc-projects/bind9!11508