This fixes the issues described in
https://github.com/rust-lang/rust/issues/136102. Primarily, this
resolves some issues with how the documentation for the prelude is
generated:
- It avoids showing "unstable" for macros in the prelude that are
actually stable.
- Avoids duplication of some pages due to the previous lack of
`doc(no_inline)`.
- Makes the different edition preludes consistent, and sets a pattern
that can be used by future editions.
We may need to rearrange these modules in the future if we decide to
remove anything from the prelude again. If we do, I think we should look
into a different solution that avoids the documentation problems.
There are some comments describing multiple subsequent `use` items. When
the big `use` reformatting happens some of these `use` items will be
reordered, possibly moving them away from the comment. With this
additional level of formatting it's not really feasible to have comments
of this type. This commit removes them in various ways:
- merging separate `use` items when appropriate;
- inserting blank lines between the comment and the first `use` item;
- outright deletion (for comments that are relatively low-value);
- adding a separate "top-level" comment.
We also entirely skip formatting for four library files that contain
nothing but `pub use` re-exports, where reordering would be painful.
rust_2015 and rust_2018 are just re-exports of v1.
rust_2021 is a module that for now just re-exports everything from v1,
such that we can add more things later.
