Support the `<verb>_parent_in_place()` API for operating on parents instead of children

## What problem does this solve or what need does it fill?

We've got [`set_parent_in_place`](https://docs.rs/bevy/0.14.0-rc.3/bevy/prelude/trait.BuildChildrenTransformExt.html#tymethod.set_parent_in_place) and [`remove_parent_in_place`](https://docs.rs/bevy/0.14.0-rc.3/bevy/prelude/trait.BuildChildrenTransformExt.html#tymethod.remove_parent_in_place) when operating on a child, but no corresponding methods when adding children to a parent.

## What solution would you like?

Duplicate [`BuildChildren`](https://docs.rs/bevy/0.14.0-rc.3/bevy/hierarchy/trait.BuildChildren.html)'s methods for `_in_place`, adding the following methods:
- `with_children_in_place`
- `add_child_in_place`
- `push_children_in_place`
- `insert_children_in_place`
- `remove_children_in_place`
- `clear_children_in_place`
- `replace_children`

if we also add `set_parent_in_place` and `remove_parent_in_place`, we can probably even remove the [`BuildChildrenTransformExt`](https://docs.rs/bevy/0.14.0-rc.3/bevy/prelude/trait.BuildChildrenTransformExt.html#tymethod.remove_parent_in_place) trait.

## What alternative(s) have you considered?

Don't add the suggested API. The desired outcome can always be achieved by limiting yourself to operating on a child or iterating over children instead of using the API on the parent.