Correctly resolve nexus_url from environment variables
- Check CAR_TMDATA_REPOSITORY_URL before CAR_RAW_REPOSITORY_URL
- If CAR_RAW_REPOSITORY_URL is used, replace
internalwithtelmodellike what is done inska-cicd-makefile.make-tmdata-support - Add explicit test of nexus returning 404 to get 100% coverage as that
was implicitly tested previously by the CI CAR_RAW_REPOSITORY_URL not
being correctly tweaked to replace
internalwithtelmodel