This fixes an issue with the following sample:

    mod foo {
	mod inaccessible {
	    pub struct X;
	}
	pub mod avail {
	    pub struct X;
	}
    }

    fn main() { X; }

Instead of suggesting both `use crate::foo::inaccessible::X;` and `use
crate::foo::avail::X;`, it should only suggest the latter.

It is done by trimming the list of suggestions from inaccessible paths
if accessible paths are present.

Visibility is checked with `is_accessible_from` now instead of being
hard-coded.

-

Some tests fixes are trivial, and others require a bit more explaining,
here are my comments:

src/test/ui/issues/issue-35675.stderr: Only needs to make the enum
public to have the suggestion make sense.

src/test/ui/issues/issue-42944.stderr: Importing the tuple struct won't
help because its constructor is not visible, so the attempted
constructor does not work. In that case, it's better not to suggest it.
The case where the constructor is public is covered in `issue-26545.rs`.

Add comment to clarify the pattern

impl PartialEq<Vec<B>> for &[A], &mut [A]

rust-lang/rfcs#2917

…rochenkov

Prefer accessible paths in 'use' suggestions

This PR addresses issue rust-lang#26454, where `use` suggestions are made for paths that don't work. For example:

```rust
mod foo {
    mod bar {
        struct X;
    }
}

fn main() { X; } // suggests `use foo::bar::X;`
```

Add E0765

…from, r=Amanieu

deprecate wrapping_offset_from

As per rust-lang#41079 (comment) which seems like a consensus.

r? @Amanieu

Miri: replace many bug! by span_bug!

r? @oli-obk

…ulacrum

Do not send a notification for P-high stable regressions

This is kind of a hack to only match nightly and beta regressions, but not stable regressions. See my tests [on the playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=6ff8a809162118aa2951f2ff12400067).

r? @spastorino cc @Mark-Simulacrum