use etchosts package from c/common

Use the new logic from c/common to create the hosts file. This will help
to better allign the hosts files between buildah and podman.

Also this fixes several bugs:
- remove host entries when container is stopped and has a netNsCtr
- add entries for containers in a pod
- do not duplicate entries in the hosts file
- use the correct slirp ip when an userns is used

Features:
- configure host.containers.internal entry in containers.conf
- configure base hosts file in containers.conf

Fixes #12003
Fixes #13224

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

vendor/github.com/containers/common/libnetwork/etchosts/util.go

@@ -0,0 +1,30 @@
+package etchosts
+
+import (
+	"fmt"
+
+	"github.com/containers/common/pkg/config"
+	securejoin "github.com/cyphar/filepath-securejoin"
+)
+
+// GetBaseHostFile return the hosts file which should be used as base.
+// The first param should be the config value config.Containers.BaseHostsFile
+// The second param should be the root path to the mounted image. This is
+// required when the user conf value is set to "image".
+func GetBaseHostFile(confValue, imageRoot string) (string, error) {
+	switch confValue {
+	case "":
+		return config.DefaultHostsFile, nil
+	case "none":
+		return "", nil
+	case "image":
+		// use secure join to prevent problems with symlinks
+		path, err := securejoin.SecureJoin(imageRoot, config.DefaultHostsFile)
+		if err != nil {
+			return "", fmt.Errorf("failed to get /etc/hosts path in image: %w", err)
+		}
+		return path, nil
+	default:
+		return confValue, nil
+	}
+}