ci: Replace binfmt container with Debian qemu-user-static

This apparently fixes sporadic crashes of arm64 image builds, see also
[1] and [2]. Ubuntu's version of qemu-user does not seem to have this
fixed yet either, therefore inject the current Debian package.

In addition, this moves away from the floating
docker.io/tonistiigi/binfmt:latest that docker/setup-qemu-action@v3
uses. This loose coupling is questionable, not only in the light of
this issue.

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1087822
[2] tonistiigi/binfmt#215

Co-Developed-by: Felix Moessbauer <felix.moessbauer@siemens.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

.github/actions/docker-init/action.yml

@@ -12,7 +12,15 @@ runs:
   using: composite
   steps:
     - name: Set up QEMU
-      uses: docker/setup-qemu-action@v3
+      shell: bash
+      env:
+        QEMU_USER_STATIC_PACKAGE: qemu-user-static_7.2+dfsg-7+deb12u12_amd64.deb
+        PACKAGE_SHA256: 1a2696081c1f30d464f79fd300196822397c77f05440ea9ce6dc8e9658b595ec
+      run: |
+        # temporarily use Debian qemu-user-static until Ubuntu fixes theirs
+        wget -q http://ftp.debian.org/debian/pool/main/q/qemu/${QEMU_USER_STATIC_PACKAGE}
+        echo "${PACKAGE_SHA256} ${QEMU_USER_STATIC_PACKAGE}" | sha256sum -c
+        sudo dpkg -i ${QEMU_USER_STATIC_PACKAGE}
 
     - name: Set up Docker Buildx
       uses: docker/setup-buildx-action@v3