Migrate yang models in monorepo

.gitmodules

.golangci.yml

Makefile

controller/api/initialise_test.go

controller/configs/ci-testing-gosdn.toml

controller/northbound/server/pnd_test.go

controller/nucleus/device_test.go

controller/nucleus/gnmi_transport.go

controller/nucleus/gnmi_transport_test.go

controller/nucleus/initialise_test.go

controller/nucleus/principalNetworkDomain.go

controller/nucleus/principalNetworkDomain_test.go

controller/nucleus/southbound.go

controller/nucleus/southbound_test.go

controller/test/integration/nucleusIntegration_test.go

controller/test/targets.go

controller/test/yang/test-module.go

controller/test/yang/yang.go

csbi/resources/csbi.go

csbi/resources/current.go.sum