RFC: Drop rustler::wrapper

[filmor]

Instead of using the intermediate half-safe function layer, we use the
enif_* functions now directly in the high level functions.

From a cursory github search, this affects the following codebases:

• https://github.com/elixir-explorer/explorer (@akoutmos)
• https://github.com/rubas/exmpeg (@rubas) (fixed in refactor: store Env<'a> instead of the raw rustler::wrapper::NIF_ENV pointer rubas/exmpeg#86)
• https://github.com/jbevemyr/yanger (@jbevemyr)
• https://github.com/Qqwy/elixir-rustler_elixir_fun (@Qqwy) (fixed in Update rustler Qqwy/elixir-rustler_elixir_fun#13)

Could you explain what you exactly drop down to rustler::wrapper functions for? Can the same be achieved through direct usage of rustler::sys or with a proper safe wrapper that simply doesn't exist yet?

[rubas]

exmpeg used rustler::wrapper::NIF_ENV only to keep the calling NIF's env in a struct without a lifetime parameter. It sends progress messages and checks caller liveness from a dirty NIF. We now store Env<'a> directly (rubas/exmpeg#86), so we do not need wrapper. Dropping it is fine for us.

[Qqwy]

#456 made the usage of rustler::wrapper superfluous for rustler_elixir_fun but I never ended up upstreaming the change until it was merged. @filmor was quicker than me to create such a PR now after opening this issue (Qqwy/elixir-rustler_elixir_fun#13). Thanks a lot for your help, and thank you very very much for your excellent work on Rustler!

[akoutmos]

Thanks for the heads up and for all your hard work! Made the appropriate changes in Explorer elixir-explorer/explorer#1164. When CI goes green I'll merge it in!