Add validation around the required values for setValueTemplates artifact names (eg: no `.`, `/`, or `-`)

As stated in https://skaffold.dev/docs/pipeline-stages/deployers/helm/#sanitizing-the-artifact-name-from-invalid-go-template-characters, setValueTemplates proper usage requires changing all `.`, `-`, and `/` charts -> `_`. We should add validation around the required values for setValueTemplates artifact names (eg: no `.`, `/`, or `-`) so that users aren't confused/know-this and don't accidentally misconfigures skaffold or have friction here