library(tidyverse) should treat tidyverse imports as Depends

[MichaelChirico]

Closely related to #2695, #2691.

After we solve #2695, we'll still get the same false positive as #2691 about mutate(), because {tidyverse} does not do package dependencies "correctly" -- it intentionally puts in Imports those packages which would elsewhere in the R ecosystem be in Depends, i.e. library(tidyverse) attaches its Imports (as opposed to just [possibly] loadNamespace() them):

tidyverse/tidyverse#40

I think {tidyverse} is basically alone in the R ecosystem in doing this, but is also extremely common in practice, so carving out some hand-curated code is IMO appropriate here.

[AshesITR]

We maintain an internal fork of tidyverse as well, doing the same kind of abuse. It would be nice if the fix had a configuration setting for tidyverse-like packages.