Move to vppcfg based configs - generate the initial config in vpp.service. Needs 20260406-2

build/bird/hvn1.lab.ipng.ch/vpp1-3/etc/vpp/config/manual-pre.vpp

@@ -0,0 +1,2 @@
+comment { Put any config for vpp1-3 you'd like here. }
+comment { It will persist across restarts of VPP and reboots of the VM. }