Support arrays in type reflection

Tracking issue: rust-lang#146922

This PR adds support for inspecting arrays `[T; N]` through type reflection. It does so by adding `TypeKind::Array` and the `Array` struct:

```rust
pub struct Array {
    pub element_ty: TypeId,
    pub len: usize,
}
```

This can be used to inspect arrays like so:

```rust
match const { Type::of::<[u16; 4]>() }.kind {
    TypeKind::Array(array) => {
        assert_eq!(array.element_ty, TypeId::of::<u16>());
        assert_eq!(array.len, 4);
    }
    _ => unreachable!(),
}
```

r? @oli-obk

Rollup of 13 pull requests

Successful merges:

 - #150587 (triagebot: add A-rustdoc-js autolabel)
 - #150677 (Improve std::path::Path::join documentation)
 - #150737 (diagnostics: make implicit Sized bounds explicit in E0277)
 - #150771 (Remove legacy homu `try` and `auto` branch mentions)
 - #150840 (Make `--print=check-cfg` output compatible `--check-cfg` arguments)
 - #150915 (Regression test for type params on eii)
 - #151017 (Port the rustc dump attributes to the attribute parser)
 - #151019 (Make `Type::of` support unsized types)
 - #151031 (Support arrays in type reflection)
 - #151043 (armv7-unknown-linux-uclibceabihf.md: Fix bootstrap.toml syntax)
 - #151052 (ui: add regression test for macro resolution ICE (issue #150711))
 - #151053 (Reduce flakyness for `tests/rustdoc-gui/notable-trait.goml`)
 - #151055 (Emit error instead of delayed bug when meeting mismatch type for const array)

r? @ghost

Rollup merge of #151031 - reflect-arrays, r=oli-obk

Support arrays in type reflection

Tracking issue: #146922

This PR adds support for inspecting arrays `[T; N]` through type reflection. It does so by adding `TypeKind::Array` and the `Array` struct:

```rust
pub struct Array {
    pub element_ty: TypeId,
    pub len: usize,
}
```

This can be used to inspect arrays like so:

```rust
match const { Type::of::<[u16; 4]>() }.kind {
    TypeKind::Array(array) => {
        assert_eq!(array.element_ty, TypeId::of::<u16>());
        assert_eq!(array.len, 4);
    }
    _ => unreachable!(),
}
```

r? @oli-obk