[9.20] chg: usr: Optimize the TCP source port selection on Linux

Enable a socket option on the outgoing TCP sockets to allow faster selection of the source <address,port> tuple for different destination <address,port> tuples when nearing over 70-80% of the source port utilization.

Backport of MR !11569

Merge branch 'backport-improve-selection-of-outgoing-TCP-port-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!11573