app/test: introduce resources for tests

app/test: introduce resources for tests

Certain internal mechanisms of DPDK access different file system
structures (e.g. /sys/bus/pci/devices). It is difficult to test
those cases automatically by a unit test when such path is not
hard-coded and there is no simple way how to distribute fake ones
with the current testing environment.

This patch adds a possibility to declare a resource embedded in
the test binary itself. The structure resource cover the generic
situation - it provides a name for lookup and pointers to the
embedded data blob. A resource is registered in a constructor by
the macro REGISTER_RESOURCE.

Some initial tests of simple resources is included and added into
the group_1.

Signed-off-by: Jan Viktorin <viktorin@rehivetech.com>