oetest.py: Add json file support to specify packages needed in runtime tests

oetest.py: Add json file support to specify packages needed in runtime tests

This adds the functionality to use a json file to
specify the packages needed for a particular test.

The content of the json file is a dictionary with
dictionaries inside, using the test name as the hash.

The json file must have the same name as the class
module name and must be in the same path.

[YOCTO #7850]

Signed-off-by: Mariano Lopez <mariano.lopez@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>