Additional improvements to delegating `.output`

[Andrew-S-Rosen]

Thanks for this @vineetbansal. I think this is a nice feature. The slight ambiguity is that this can only be used for jobs which report dictionaries/other objects, and you only want to access one attribute/item/field. In the future, it would be nice if this could be used as:

@job
def make_str(s):
    return s

@job
def capitalize(s):
    return s.upper()

job1 = make_str("world")
job2 = capitalize(job1)

flow = Flow([job1, job2])

I'm not sure how much trouble that will be to implement. I'm happy to merge this for now but I'm interested if this use case is also of interest for @Andrew-S-Rosen?

Originally posted by @utf in #845 (comment)

[utf]

Another thought is that potentially we should add similar logic getitem logic to Flow, as these can often be used interchangeably with Jobs.