[24.0 backport] c8d: Fix building Dockerfiles that have FROM scratch

[thaJeztah]

• backport of c8d: Fix building Dockerfiles that have FROM scratch #46284
• Fixes: containerd-integration: classic builder fails when building FROM scratch #46248
• addresses [bug] Cannot build with DOCKER_BUILDKIT=0 docker/for-mac#6853 (comment)

- What I did
Fix running containers with empty Image.

- How I did it
See commits.

- How to verify it
c8d integration tests (#45232) from TestDockerCLIBuildSuite:

- DONE 250 tests, 13 skipped, 58 failures in 352.552s
+ DONE 250 tests, 13 skipped, 42 failures in 406.027s

Before

$ printf 'FROM scratch\nLABEL asdf=1' | DOCKER_BUILDKIT=0 docker build -t asdf -
DEPRECATED: The legacy builder is deprecated and will be removed in a future release.
            BuildKit is currently disabled; enable it by removing the DOCKER_BUILDKIT=0
            environment-variable.

Sending build context to Docker daemon  2.048kB
Step 1/2 : FROM scratch
 --->
Step 2/2 : LABEL asdf=1
invalid reference format

After

$ printf 'FROM scratch\nLABEL asdf=1' | DOCKER_BUILDKIT=0 docker build -t asdf -
DEPRECATED: The legacy builder is deprecated and will be removed in a future release.
            BuildKit is currently disabled; enable it by removing the DOCKER_BUILDKIT=0
            environment-variable.

Sending build context to Docker daemon  2.048kB
Step 1/2 : FROM scratch
 --->
Step 2/2 : LABEL asdf=1
 ---> Running in 08bc1d65adb1
 ---> Removed intermediate container 08bc1d65adb1
 ---> 7072ecaf239f
Successfully built 7072ecaf239f
Successfully tagged asdf:latest

- Description for the changelog

containerd integration: Fix building Dockerfiles with `FROM scratch` instruction when using the legacy builder (non buildkit).

- A picture of a cute animal (not mandatory but encouraged)