E2E: add test for the unnumbered BGP peering

The test requires point-to-point connection so we cannot use any
existing infra peer. Therefore a new peer (docker container)
runs with no network, and point-to-point connections are created using
`sudo ip` commands.

There are three specs
```
Unnumbered BGP session is established and routes are verified iBGP
Unnumbered BGP session is established and routes are verified eBGP
```

Signed-off-by: karampok <karampok@gmail.com>

e2etests/e2etest_suite_test.go

@@ -47,6 +47,7 @@ func handleFlags() {
 		runOnHost = true
 	}
 	dump.ReportPath = reportPath
+	tests.FRRImage = frrImage
 }
 
 func TestMain(m *testing.M) {

e2etests/go.mod

@@ -11,6 +11,7 @@ replace (
 )
 
 require (
+	github.com/google/go-cmp v0.6.0
 	github.com/metallb/frr-k8s v0.0.16
 	github.com/onsi/ginkgo/v2 v2.19.0
 	github.com/onsi/gomega v1.33.1
@@ -51,7 +52,6 @@ require (
 	github.com/golang/protobuf v1.5.4 // indirect
 	github.com/google/btree v1.0.1 // indirect
 	github.com/google/gnostic-models v0.6.8 // indirect
-	github.com/google/go-cmp v0.6.0 // indirect
 	github.com/google/gofuzz v1.2.0 // indirect
 	github.com/google/pprof v0.0.0-20240525223248-4bfdf5a9a2af // indirect
 	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 // indirect