bugfix : skip doc(hidden) default members
fixes #14957 . I have two questions :
1. I am definitely looking for a more idiomatic way for the things I added in `crates/ide-assists/src/utils.rs`. See `FIXME` in that file.
2. Would it be actually better to change `DefaultMethods` to something like
```rust
enum DefaultMethods {
Only( IgnoreHidden ( bool ) ) ,
None
}
```
instead of adding a boolean to every function that calls `crates/ide-assists/src/utils.rs::filter_assoc_items`
efc5a813de