split up make_function_list.R

[EmilHvitfeldt]

This PR refactors make_function_lists.R script into one script for each table corresponding to the tables seen on https://www.tidymodels.org/find/.

• Split make_function_lists.R into separate scripts in make_function_lists/:
  • _utils.R - shared utilities and caching logic
  • broom.R, recipes.R, tidymodels.R, parsnip.R, sparse.R, tidyclust.R - one for each table
  • run_all.R - runs all of them (same as running make_function_list.R)

I replace pkgdown::as_pkgdown() with direct Rd file parsing via tools::parse_Rd().

The more important change is the implementation of caching. We now store a cache of the things we are fetching in .pkg_cache.csv. Reducing the total time taken to run all of this down to around 3 minutes.
Notice we are still fetching things from websites, so this is still not static.

[EmilHvitfeldt]

I don't know if this is too much or not. It increases the complexity