Consider doing end-to-end Openconfig to ChassisConfig conversion tests

[pudelkoM]

The openconfig converter tests currently use issue specific tests files, but not full config examples. A test should have both formats available and should verify conversion in both directions.

This original version demonstrates one direction: https://github.com/stratum/stratum/blob/a818b13bb4372a5fd7752f0ffa6933a6abe1e517/stratum/hal/lib/common/openconfig_converter_test.cc#L12-L22

We did not get the test data files in the original code drop, but recreating them now should not be too hard.

[bocon13]

We should put an oc_device.pb.txt in each hal/config/ directory. Then just test all of them.

This makes sure that we keep them in sync.