CLI: use global image version field

- Restructure config by removing CSP-specific image references
- Add global image field
- Download image lookup table on create
- Download QEMU image on QEMU create

cli/internal/cloudcmd/clients.go

@@ -8,9 +8,11 @@ package cloudcmd
 
 import (
 	"context"
+	"io"
 
 	"github.com/edgelesssys/constellation/v2/cli/internal/terraform"
 	"github.com/edgelesssys/constellation/v2/internal/cloud/cloudprovider"
+	"github.com/edgelesssys/constellation/v2/internal/config"
 )
 
 type terraformClient interface {
@@ -25,3 +27,11 @@ type libvirtRunner interface {
 	Start(ctx context.Context, containerName, imageName string) error
 	Stop(ctx context.Context) error
 }
+
+type imageFetcher interface {
+	FetchReference(ctx context.Context, config *config.Config) (string, error)
+}
+
+type rawDownloader interface {
+	Download(ctx context.Context, errWriter io.Writer, isTTY bool, source, version string) (string, error)
+}