Rename debian.interfaces to ifupdown

When I first split the debian interfaces support from wwinit, I was unable to
figure out what it was called. I used the inelegant name "debian.interfaces" to
identify it; but I have since learned that it is called "ifupdown." I have
since learned that there is even a variant implementation, ifupdown-ng, that is
used by Alpine Linux.

This PR renames the overlay to ifupdown, but retains a copy of it at
debian.interfaces for backwards compatibility.

Signed-off-by: Jonathon Anderson <janderson@ciq.com>

internal/pkg/upgrade/node_test.go

@@ -638,8 +638,8 @@ nodeprofiles:
       - udev.netname
       - systemd.netname
       - ifcfg
+      - ifupdown
       - NetworkManager
-      - debian.interfaces
       - wicked
       - ignition
     kernel:
@@ -781,8 +781,8 @@ nodeprofiles:
       - udev.netname
       - systemd.netname
       - ifcfg
+      - ifupdown
       - NetworkManager
-      - debian.interfaces
       - wicked
       - ignition
 nodes:
@@ -802,8 +802,8 @@ nodes:
       - udev.netname
       - systemd.netname
       - ifcfg
+      - ifupdown
       - NetworkManager
-      - debian.interfaces
       - wicked
       - ignition
 `,
@@ -830,8 +830,8 @@ nodeprofiles:
       - udev.netname
       - systemd.netname
       - ifcfg
+      - ifupdown
       - NetworkManager
-      - debian.interfaces
       - wicked
       - ignition
 nodes:
@@ -851,8 +851,8 @@ nodes:
       - udev.netname
       - systemd.netname
       - ifcfg
+      - ifupdown
       - NetworkManager
-      - debian.interfaces
       - wicked
       - ignition
 `,
@@ -874,8 +874,8 @@ nodeprofiles:
       - udev.netname
       - systemd.netname
       - ifcfg
+      - ifupdown
       - NetworkManager
-      - debian.interfaces
       - wicked
       - ignition
 nodes:
@@ -895,8 +895,8 @@ nodes:
       - udev.netname
       - systemd.netname
       - ifcfg
+      - ifupdown
       - NetworkManager
-      - debian.interfaces
       - wicked
       - ignition
 `,
@@ -1076,8 +1076,8 @@ nodeprofiles:
       - udev.netname
       - systemd.netname
       - ifcfg
+      - ifupdown
       - NetworkManager
-      - debian.interfaces
       - wicked
       - ignition
     kernel: