test/py: Add tests for the erofs

Add Python scripts to test 'ls' and 'load' commands, as well as
test related filesystem functions.

Signed-off-by: Huang Jianan <jnhuang95@gmail.com>

tools/docker/Dockerfile

@@ -48,6 +48,7 @@ RUN apt-get update && apt-get install -y \
 	dosfstools \
 	e2fsprogs \
 	efitools \
+	erofs-utils \
 	expect \
 	fakeroot \
 	flex \