[9.20] fix: usr: Fix long-running incoming transfers

Incoming transfers that took longer than 30 seconds would stop reading from the TCP stream and the incoming transfer would be indefinitely stuck causing BIND 9 to hang during shutdown.

This has been fixed and the `max-transfer-time-in` and `max-transfer-idle-in` timeouts are now honoured.

Closes #4949

Backport of MR !9531

Merge branch 'backport-4949-fix-ignored-and-invalid-dispatch-timeout-in-dns_xfrin-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!9536