Instead of having a generic "virt_qemu" board use "virt_qemu_<arch>" in
order to have a clean distinction between boards. Current supported
boards are "virt_qemu_arm_v7a", "virt_qemu_arm_v8a", and
"virt_qemu_riscv".
issue #4034
* Remove SPEC declarations from mk/spec
* Remove all board-specific REQUIRE declaratiions left
* Replace [have_spec <board>] run-script declarations with have_board where necessary
* Remove addition of BOARD variable to SPECS in toplevel Makefile
* Move board-specific directories in base-hw out of specs
Let the NIC router provide an Uplink service besides the Nic service that it
already provided. Requests for an Uplink session towards the NIC router are
assigned to Domains using the same <policy> configuration tags that are used in
order to assign Nic session requests. The MAC addresses of Uplink session
components are _NOT_ considered during the allocation of MAC addresses for NIC
session components at the same Domain. The task of avoiding MAC address clashes
between Uplink session components and Nic session components is therefore left
to the integrator. Apart from that, Uplink session components are treated by
the NIC router like any other interface.
Ref #3961
* Introduce 'use_arp' configuration flag at the NIC router in order to disable
requesting IP-to-MAC address resolutions via ARP for domains.
* Add automated run/nic_router_disable_arp test to the autopilot that tests
the effect of the new flag
* Document the new flag and the new test in the NIC router README
Fixes#3935
