test: env: add test for env info sub-command

test: env: add test for env info sub-command

Add a pytest for testing the env info sub-command:

test_env_info: test command with several option that
can be executed on real hardware device without assumption

test_env_info_sandbox: test the result on sandbox
with a known ENV configuration: ready & default & persistent

The quiet option '-q' is used for support in shell test;
for example:
  if env info -p -d -q; then env save; fi

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Acked-by: Stephen Warren <swarren@nvidia.com>