feat: IETF Network Slice mock added

src/tests/tools/mock_ietf_network_slice_sdn_ctrl/Dockerfile

...etf_network_slice_sdn_ctrl/MockIetfNetworkSliceSdnCtrl.py

src/tests/tools/mock_ietf_network_slice_sdn_ctrl/README.md

...k_ietf_network_slice_sdn_ctrl/ResourceConnectionGroups.py

...mock_ietf_network_slice_sdn_ctrl/ResourceNetworkSlices.py

src/tests/tools/mock_ietf_network_slice_sdn_ctrl/__init__.py

src/tests/tools/mock_ietf_network_slice_sdn_ctrl/build.sh

src/tests/tools/mock_ietf_network_slice_sdn_ctrl/deploy.sh

...work_slice_sdn_ctrl/mock-ietf-network-slice-sdn-ctrl.yaml

...ts/tools/mock_ietf_network_slice_sdn_ctrl/requirements.in

src/tests/tools/mock_ietf_network_slice_sdn_ctrl/run.sh