tiltfile: resources with extra pod selectors or images should be considered workloads

[nicks]

Hello @jazzdan,

Please review the following commits I made in branch nicks/nonworkload:

993df2b (2020-07-07 12:30:59 -0400)
tiltfile: resources with extra pod selectors or images should be considered workloads

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[nicks]

I wonder if we should change the terminology here to "Podless" or something, since that what it means in practice (We don't track pods for nonworkloads)