Remove WorldCell (#12551)

# Objective
Fixes #12549. WorldCell's support of everything a World can do is
incomplete, and represents an alternative, potentially confusing, and
less performant way of pulling multiple fetches from a `World`. The
typical approach is to use `SystemState` for a runtime cached and safe
way, or `UnsafeWorldCell` if the use of `unsafe` is tolerable.

## Solution
Remove it!

---

## Changelog
Removed: `WorldCell`
Removed: `World::cell`

## Migration Guide
`WorldCell` has been removed. If you were using it to fetch multiple
distinct values from a `&mut World`, use `SystemState` by calling
`SystemState::get` instead. Alternatively, if `SystemState` cannot be
used, `UnsafeWorldCell` can instead be used in unsafe contexts.

crates/bevy_ecs/src/world/mod.rs

@@ -6,7 +6,6 @@ mod entity_ref;
 pub mod error;
 mod spawn_batch;
 pub mod unsafe_world_cell;
-mod world_cell;
 
 pub use crate::change_detection::{Mut, Ref, CHECK_TICK_THRESHOLD};
 pub use crate::world::command_queue::CommandQueue;
@@ -16,7 +15,6 @@ pub use entity_ref::{
  OccupiedEntry, VacantEntry,
 };
 pub use spawn_batch::*;
-pub use world_cell::*;
 
 use crate::{
  archetype::{ArchetypeComponentId, ArchetypeId, ArchetypeRow, Archetypes},
@@ -111,8 +109,6 @@ pub struct World {
  pub(crate) storages: Storages,
  pub(crate) bundles: Bundles,
  pub(crate) removed_components: RemovedComponentEvents,
- /// Access cache used by [`WorldCell`]. Is only accessed in the `Drop` impl of `WorldCell`.
- pub(crate) archetype_component_access: ArchetypeComponentAccess,
  pub(crate) change_tick: AtomicU32,
  pub(crate) last_change_tick: Tick,
  pub(crate) last_check_tick: Tick,
@@ -129,7 +125,6 @@ impl Default for World {
  storages: Default::default(),
  bundles: Default::default(),
  removed_components: Default::default(),
- archetype_component_access: Default::default(),
  // Default value is `1`, and `last_change_tick`s default to `0`, such that changes
  // are detected on first system runs and for direct world queries.
  change_tick: AtomicU32::new(1),
@@ -217,13 +212,6 @@ impl World {
  &self.removed_components
  }
 
- /// Retrieves a [`WorldCell`], which safely enables multiple mutable World accesses at the same
- /// time, provided those accesses do not conflict with each other.
- #[inline]
- pub fn cell(&mut self) -> WorldCell<'_> {
- WorldCell::new(self)
- }
-
  /// Creates a new [`Commands`] instance that writes to the world's command queue
  /// Use [`World::flush_commands`] to apply all queued commands
  #[inline]

crates/bevy_ecs/src/world/unsafe_world_cell.rs

@@ -4,7 +4,7 @@
 
 use super::{command_queue::CommandQueue, Mut, Ref, World, WorldId};
 use crate::{
- archetype::{Archetype, ArchetypeComponentId, Archetypes},
+ archetype::{Archetype, Archetypes},
  bundle::Bundles,
  change_detection::{MutUntyped, Ticks, TicksMut},
  component::{ComponentId, ComponentTicks, Components, StorageType, Tick, TickCells},
@@ -284,36 +284,6 @@ impl<'w> UnsafeWorldCell<'w> {
  &unsafe { self.unsafe_world() }.storages
  }
 
- /// Shorthand helper function for getting the [`ArchetypeComponentId`] for a resource.
- #[inline]
- pub(crate) fn get_resource_archetype_component_id(
- self,
- component_id: ComponentId,
- ) -> Option<ArchetypeComponentId> {
- // SAFETY:
- // - we only access world metadata
- let resource = unsafe { self.world_metadata() }
- .storages
- .resources
- .get(component_id)?;
- Some(resource.id())
- }
-
- /// Shorthand helper function for getting the [`ArchetypeComponentId`] for a resource.
- #[inline]
- pub(crate) fn get_non_send_archetype_component_id(
- self,
- component_id: ComponentId,
- ) -> Option<ArchetypeComponentId> {
- // SAFETY:
- // - we only access world metadata
- let resource = unsafe { self.world_metadata() }
- .storages
- .non_send_resources
- .get(component_id)?;
- Some(resource.id())
- }
-
  /// Retrieves an [`UnsafeEntityCell`] that exposes read and write operations for the given `entity`.
  /// Similar to the [`UnsafeWorldCell`], you are in charge of making sure that no aliasing rules are violated.
  #[inline]