First part of a BVI refactor

The handling of BVI is awkward, with the autoderived interface name
"bviXX" based on the bridgedomain bd_id. Lots of special casing happens
on account of this decision, and to make matters worse there is poor
interaction (leading to VPP crashes) when BVIs and Loopbacks are used
at the same time: https://lists.fd.io/g/vpp-dev/message/21116

This is step one of a refactor of the logic. In this commit, I'm
removing all of the BVI logic from the codebase, rendering bridgedomains
unable to have IP interfaces. In the next commit, I will introduce new
behavior in the schema, allowing for 'bvi' to be a loopback
interfacename which will be used as BVI for a bridgedomain, restoring
the ability to use bridgedomains with IP interfaces (using a loop).

unittest/test_bridgedomain.yaml

@@ -44,13 +44,10 @@ bridgedomains:
     mtu: 3000
     interfaces: [ GigabitEthernet1/0/0, GigabitEthernet1/0/1, BondEthernet0 ]
   bd11:
-    description: "Bridge Domain 11, both LCP and address"
+    description: "Bridge Domain 11, with sub-interfaces"
     mtu: 2000
     interfaces: [ GigabitEthernet2/0/0.100, GigabitEthernet2/0/1.100, BondEthernet0.100 ]
-    lcp: "bvi123456789012"
-    addresses: [ 192.0.2.1/29, 2001:db8::1/64 ]
   bd12:
     description: "Bridge Domain 12, invalid because it has Gi1/0/0 as well"
     mtu: 9000
     interfaces: [ GigabitEthernet4/0/0, GigabitEthernet1/0/0 ]
-    lcp: "bvi12"

unittest/yaml/correct-address.yaml

@@ -29,6 +29,4 @@ bridgedomains:
   bd10:
     description: "Bridge Domain 10"
     mtu: 2000
-    lcp: "bvi10"
-    addresses: [ 10.0.0.2/32, 2001:db8::2/128 ]
     interfaces: [ GigabitEthernet3/0/0 ]

unittest/yaml/correct-bridgedomain.yaml

@@ -46,15 +46,8 @@ bridgedomains:
     mtu: 3000
     interfaces: [ GigabitEthernet1/0/0, GigabitEthernet1/0/1, BondEthernet0 ]
   bd11:
-    description: "Bridge Domain 11, both LCP and address"
+    description: "Bridge Domain 11"
     mtu: 2000
-    interfaces: [ GigabitEthernet2/0/0.100, GigabitEthernet2/0/1.100, BondEthernet0.100 ]
-    lcp: "bvi123456789012"
-    addresses: [ 192.0.2.1/29, 2001:db8::1/64 ]
+    interfaces: [ GigabitEthernet2/0/0.100, GigabitEthernet2/0/1.100 ]
   bd12:
-    description: "Bridge Domain 12, LCP but no address"
-    mtu: 9000
-    interfaces: [ GigabitEthernet4/0/0, GigabitEthernet4/0/1 ]
-    lcp: "bvi12"
-  bd13:
-    description: "Bridge Domain 13, it is OK to have no member interfaces"
+    description: "Bridge Domain 12, it is OK to have no member interfaces"

unittest/yaml/correct-example1.yaml

@@ -71,6 +71,4 @@ bridgedomains:
   bd10:
     description: "Bridge Domain 10"
     mtu: 1500
-    lcp: "bvi10"
-    addresses: [ 192.0.2.9/29, 2001:db8:2::1/64 ]
     interfaces: [ BondEthernet0.203, GigabitEthernet3/0/0 ]

unittest/yaml/error-address1.yaml

@@ -5,8 +5,7 @@ test:
       - "interface .* IP address .* conflicts with another"
       - "sub-interface .* IP address .* conflicts with another"
       - "loopback .* IP address .* conflicts with another"
-      - "bridgedomain .* IP address .* conflicts with another"
-    count: 18
+    count: 14
 ---
 interfaces:
   GigabitEthernet1/0/0:
@@ -27,8 +26,6 @@ interfaces:
 
   GigabitEthernet1/0/2:
     lcp: e0-2
-    description: "These addresses overlap with bd1"
-    addresses: [ 192.0.2.18/29, 2001:db8:3::2/64 ]
 
   GigabitEthernet1/0/3:
     lcp: e0-3
@@ -54,11 +51,3 @@ loopbacks:
     description: "These addresses overlap with Gi1/0/1.101"
     lcp: "loop0"
     addresses: [ 192.0.2.9/29, 2001:db8:2::1/64 ]
-
-bridgedomains:
-  bd1:
-    description: "These addresses overlap with Gi1/0/2"
-    mtu: 2000
-    lcp: "bvi1"
-    addresses: [ 192.0.2.17/29, 2001:db8:3::1/64 ]
-    interfaces: [ GigabitEthernet3/0/0 ]

unittest/yaml/error-bridgedomain5.yaml

@@ -1,19 +0,0 @@
-test:
-  description: "A bridgedomain with a BVI address must have an LCP"
-  errors:
-    expected:
-     - "bridgedomain .* has an address but no LCP"
-    count: 1
----
-interfaces:
-  GigabitEthernet1/0/0:
-    mtu: 3000
-  GigabitEthernet1/0/1:
-    mtu: 3000
-
-bridgedomains:
-  bd13:
-    description: "Bridge Domain 13, address but no LCP"
-    mtu: 3000
-    interfaces: [ GigabitEthernet1/0/0, GigabitEthernet1/0/1 ]
-    addresses: [ 192.0.2.9/29, 2001:db8:1::1/64 ]

unittest/yaml/error-lcp-unique2.yaml

@@ -4,9 +4,8 @@ test:
     expected:
      - "interface .* does not have a unique LCP name"
      - "loopback .* does not have a unique LCP name"
-     - "bridgedomain .* does not have a unique LCP name"
      - "bridgedomain bd0 is reserved"
-    count: 4
+    count: 3
 ---
 interfaces:
   GigabitEthernet1/0/0:
@@ -24,5 +23,4 @@ loopbacks:
 bridgedomains:
   bd0:
     description: "bd_id 0 in VPP is reserved"
-    lcp: "e1"
     interfaces: [ GigabitEthernet2/0/0, GigabitEthernet2/0/1 ]