Move cloud metadata packages and kubernetes resources marshaling to internal

Decouples cloud provider metadata packages from kubernetes related code

Signed-off-by: Malte Poll <mp@edgeless.systems>

internal/cloud/gcp/writer.go

@@ -0,0 +1,20 @@
+package gcp
+
+import (
+	"fmt"
+
+	"github.com/spf13/afero"
+)
+
+// Writer implements ConfigWriter.
+type Writer struct {
+	fs afero.Afero
+}
+
+// WriteGCEConf persists the GCE config on disk.
+func (w *Writer) WriteGCEConf(config string) error {
+	if err := w.fs.WriteFile("/etc/gce.conf", []byte(config), 0o644); err != nil {
+		return fmt.Errorf("writing gce config: %w", err)
+	}
+	return nil
+}