[refactor-js] refactor to new implementation

- Some changes stemming from #1854
- reorder imports
- changes to env var prefixes + id generation
- Abstraction over Jobset Spec
- Create general abstraction and copy style of how we create jobspec for native k8s jobs.
- simplified the implementation.
- similar pattern/trend to follow for argo
- remove older implementation
- @parallel metadata from k8s decorator
    - added attempt to MetaDatum tags
    - We didn't have this earlier