ci: Use qemu-user through container engine

ci/test/00_setup_env_s390x.sh

@@ -7,18 +7,9 @@
 export LC_ALL=C.UTF-8
 
 export HOST=s390x-linux-gnu
-# The host arch is unknown, so we run the tests through qemu.
-# If the host is s390x and wants to run the tests natively, it can set QEMU_USER_CMD to the empty string.
-if [ -z ${QEMU_USER_CMD+x} ]; then export QEMU_USER_CMD="${QEMU_USER_CMD:-"qemu-s390x"}"; fi
 export PACKAGES="python3-zmq"
-if [ -n "$QEMU_USER_CMD" ]; then
-  # Likely cross-compiling, so install the needed gcc and qemu-user
-  export DPKG_ADD_ARCH="s390x"
-  export PACKAGES="$PACKAGES g++-s390x-linux-gnu qemu-user libc6:s390x libstdc++6:s390x"
-fi
-# Use debian to avoid 404 apt errors
 export CONTAINER_NAME=ci_s390x
-export CI_IMAGE_NAME_TAG="debian:bookworm"
+export CI_IMAGE_NAME_TAG="docker.io/s390x/debian:bookworm"
 export TEST_RUNNER_ENV="LC_ALL=C"
 export TEST_RUNNER_EXTRA="--exclude feature_init,rpc_bind,feature_bind_extra"  # Excluded for now, see https://github.com/bitcoin/bitcoin/issues/17765#issuecomment-602068547
 export RUN_FUNCTIONAL_TESTS=true