jianchen-g

adding test files for 400G ZR++ low power mode and performance metrics tests

2

These two files have the same functional tests as the following two ZR optic testing files: https://github.com/openconfig/featureprofiles/blob/main/feature/platform/transceiver/low_power_mode/tests/zr_low_power_mode_test/zr_low_power_mode_test.go https://github.com/openconfig/featureprofiles/blob/main/feature/platform/transceiver/performance_metrics/tests/zr_pm_test/zr_pm_test.go Main differences: 1. optics PMD, operational mode, Tx power 2. clean up...