autodoc: show more doc comments for namespaces and types

previously, in the container view (the type of view that you see when
you look at `std` for example), when listing types and namespaces, we
would only show doc comments places on the direct child decl, which in
the case of the `std` namespace, for example, it's just a bunch of
re-exports.

now, if we don't find a direct doc comment, we chase indirection and
display doc comments placed directly on the definition, if any.

this is the precise priority order:

```
/// 1
pub const Foo = _Foo;

/// 2
const _Foo = struct {
   //! 3
};
```
The numbers show the priority order for autodoc.

0 files changed, 0 insertions, 0 deletions