feat(ecs): add EntityEntryCommands::entity() method chaining (#17580)

This allows you to continue chaining method calls after calling
`EntityCommands::entry`:

```rust
commands
    .entity(player.entity)
    .entry::<Level>()
    // Modify the component if it exists
    .and_modify(|mut lvl| lvl.0 += 1)
    // Otherwise insert a default value
    .or_insert(Level(0))
    // Return the EntityCommands for the entity
    .entity()
    // And continue chaining method calls
    .insert(Name::new("Player"));
```

---------

Signed-off-by: Jean Mertz <git@jeanmertz.com>

crates/bevy_ecs/src/system/commands/mod.rs

@@ -2169,6 +2169,38 @@ impl<'a, T: Component> EntityEntryCommands<'a, T> {
             .queue(entity_command::insert_from_world::<T>(InsertMode::Keep));
         self
     }
+
+    /// Get the [`EntityCommands`] from which the [`EntityEntryCommands`] was initiated.
+    ///
+    /// This allows you to continue chaining method calls after calling [`EntityCommands::entry`].
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use bevy_ecs::prelude::*;
+    /// # #[derive(Resource)]
+    /// # struct PlayerEntity { entity: Entity }
+    /// #[derive(Component)]
+    /// struct Level(u32);
+    ///
+    /// fn level_up_system(mut commands: Commands, player: Res<PlayerEntity>) {
+    ///     commands
+    ///         .entity(player.entity)
+    ///         .entry::<Level>()
+    ///         // Modify the component if it exists
+    ///         .and_modify(|mut lvl| lvl.0 += 1)
+    ///         // Otherwise insert a default value
+    ///         .or_insert(Level(0))
+    ///         // Return the EntityCommands for the entity
+    ///         .entity()
+    ///         // And continue chaining method calls
+    ///         .insert(Name::new("Player"));
+    /// }
+    /// # bevy_ecs::system::assert_is_system(level_up_system);
+    /// ```
+    pub fn entity(&mut self) -> EntityCommands {
+        self.entity_commands.reborrow()
+    }
 }
 
 #[cfg(test)]
@@ -2258,6 +2290,10 @@ mod tests {
         commands.entity(entity).entry::<W<String>>().or_from_world();
         queue.apply(&mut world);
         assert_eq!("*****", &world.get::<W<String>>(entity).unwrap().0);
+        let mut commands = Commands::new(&mut queue, &world);
+        let id = commands.entity(entity).entry::<W<u64>>().entity().id();
+        queue.apply(&mut world);
+        assert_eq!(id, entity);
     }
 
     #[test]