unsafe_op_in_unsafe_fn
Fixes #125875.
deprecated_safe
It warns about usages of `std::env::{set_var, remove_var}` with an automatic fix wrapping the call in an `unsafe` block.
std::env::{set_var, remove_var}
Allow calling these functions without `unsafe` blocks in editions up until 2021, but don't trigger the `unused_unsafe` lint for `unsafe` blocks containing these functions. Fixes #27970. Fixes #90308. CC #124866.