Add a method to bulk insert/remove components in a single archetype move

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

Minimizing archetype moves is a good target for improving performance, but we currently need to do multiple if some components need to be inserted and some need to be removed.

## What solution would you like?

We could provide a method like `world.entity_mut(e1).mutator()`, where `mutator()` would return a RAII-like object that allows the user to queue up operations to be performed, which are applied when the object is dropped:

```rust
impl EntityWorldMut {
pub fn mutator(&mut self) -> EntityMutator<'_>;
}

pub struct EntityMutator<'w, 'a> {
entity: EntityWorldMut<'w>,
// Probably can't store BundleInserters directly, but its to get the idea across
inserts: SmallVec<[BundleInserter; 8]>,
removes: SmallVec<[BundleId; 8]>,
}

impl EntityMutator<'_, '_> {
pub fn insert(&mut self, bundle: T) -> &mut self;
pub fn remove(&mut self) -> &mut Self;
pub fn insert_by_id(&mut self, id: ComponentId, ptr: OwningPtr<'_>) -> &mut Self;
pub fn remove_by_id(&mut self, id: ComponentId) -> &mut Self;
}

impl Drop for EntityMutator<'_, '_> {
fn drop(&mut self) {
// We would actually perform the changes here, on drop
}
}
```

## What alternative(s) have you considered?

Continue generating multiple archetype moves.

## Additional context

[Initial discussion on the Discord server](https://discord.com/channels/691052431525675048/749335865876021248/1297324917666086973).

Start with the proposed EntityWorldMut::mutator API and the EntityMutator, BundleInserter, Bundle, BundleId, ComponentId, and OwningPtr concepts named in the issue. Review the linked Discord discussion before deciding the API and lifecycle semantics. Done means an agreed implementation can queue component inserts and removals and apply them in a single archetype move.

Written by the indexing model from the issue text.