Merge #813

813: Add support for container_name in workspace/symbol query r=matklad a=vipentti

Currently this does not fill in the container_info if a type is defined on the top level in a file.

e.g. `foo.rs`
```rust
enum Foo { }
```
`Foo` will have None as the container_name, however

```rust
mod foo_mod {
    enum Foo { }
}
```
`Foo` has `foo_mod` as the container_name.

This closes #559

Co-authored-by: Ville Penttinen <villem.penttinen@gmail.com>