Update docker/build-push-action action to v7 #311

Job	Run time
docker_build (ubuntu-24.04, linux/amd64, amd64)	3m 26s
clippy_and_test (ubuntu-24.04-arm, linux/arm64, arm64)	51s
clippy_and_test (ubuntu-24.04, linux/amd64, amd64)	46s
docker_build (ubuntu-24.04-arm, linux/arm64, arm64)	3m 45s
release_linux	0s
docker_merge	0s
	8m 48s

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