command_ut: test: Move test into lib

command_ut: test: Move test into lib

This test doesn't belong at the top level. Move it into the lib/
directory, since that is where compression is implemented.

Rename it to just 'command', since it is obviously a unit test and the
_ut suffix does not add much except to make it different from the names
of other test files.

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Tom Rini <trini@konsulko.com> # rpi_3, rpi_4, rpi_arm64, am64x_evm_a53, am64-sk