Add support for meta-packages like `library(tidyverse)`

[lionel-]

Currently Oak doesn't understand that these packages attach other packages to the search path because these are not listed in Depends:: https://github.com/cran/tidyverse/blob/ddc25807d108573956185472213bcdfc17660204/DESCRIPTION#L17

Ideally we'd add support for a declare() annotation that describes what happens in .onAttach(): https://github.com/cran/tidyverse/blob/ddc25807d108573956185472213bcdfc17660204/R/zzz.R#L1. For now we can just hardcode the semantics for tidyverse and tidymodels.