Despawn and despawn_recursive benchmarks

[rudderbucky]

Objective

Add despawn and despawn_recursive benchmarks in a similar vein to the spawn benchmark.

Testing

Ran cargo bench from benches and it compiled fine.

On my machine:

despawn_world/1_entities
                        time:   [3.1495 ns 3.1574 ns 3.1652 ns]
Found 4 outliers among 100 measurements (4.00%)
  3 (3.00%) high mild
  1 (1.00%) high severe
despawn_world/10_entities
                        time:   [28.629 ns 28.674 ns 28.720 ns]
Found 3 outliers among 100 measurements (3.00%)
  2 (2.00%) high mild
  1 (1.00%) high severe
despawn_world/100_entities
                        time:   [286.95 ns 287.41 ns 287.90 ns]
Found 5 outliers among 100 measurements (5.00%)
  5 (5.00%) high mild
despawn_world/1000_entities
                        time:   [2.8739 µs 2.9001 µs 2.9355 µs]
Found 7 outliers among 100 measurements (7.00%)
  1 (1.00%) high mild
  6 (6.00%) high severe
despawn_world/10000_entities
                        time:   [28.535 µs 28.617 µs 28.698 µs]
Found 2 outliers among 100 measurements (2.00%)
  1 (1.00%) high mild
  1 (1.00%) high severe

despawn_world_recursive/1_entities
                        time:   [5.2270 ns 5.2507 ns 5.2907 ns]
Found 11 outliers among 100 measurements (11.00%)
  1 (1.00%) low mild
  6 (6.00%) high mild
  4 (4.00%) high severe
despawn_world_recursive/10_entities
                        time:   [57.495 ns 57.590 ns 57.691 ns]
Found 2 outliers among 100 measurements (2.00%)
  1 (1.00%) low mild
  1 (1.00%) high mild
despawn_world_recursive/100_entities
                        time:   [514.43 ns 518.91 ns 526.88 ns]
Found 4 outliers among 100 measurements (4.00%)
  1 (1.00%) high mild
  3 (3.00%) high severe
despawn_world_recursive/1000_entities
                        time:   [5.0362 µs 5.0463 µs 5.0578 µs]
Found 7 outliers among 100 measurements (7.00%)
  2 (2.00%) high mild
  5 (5.00%) high severe
despawn_world_recursive/10000_entities
                        time:   [51.159 µs 51.603 µs 52.215 µs]
Found 9 outliers among 100 measurements (9.00%)
  3 (3.00%) high mild
  6 (6.00%) high severe

[alice-i-cecile]

I feel like we should actually create some hierarchies in the despawn_recursive benchmark :)

[rudderbucky]

I feel like we should actually create some hierarchies in the despawn_recursive benchmark :)

@alice-i-cecile done

[jrobsonchase]

LGTM as well!

If I were to add more cases, it might be interesting to see the difference between deep vs wide hierarchies with the same number of entities rather than just one immediate child.