Use global borrow flags to avoid per-archetype borrow checking overhead.

[adamreichold]

This reduces the number of dynamic borrow checks to one per component instead of one per archetype, thereby avoiding dynamic allocations for the reference wrappers.

However, it also means that e.g. World::get_mut can now fail due overlapping borrows for entities in different archetypes which would have worked before.

[ghost]

Tested this using swifco-rs and it does work. Performance improvements are hardly measurable though, i.e. from

Benchmark #1: python3 test.py
  Time (mean ± σ):      3.409 s ±  0.106 s    [User: 3.572 s, System: 0.881 s]
  Range (min … max):    3.260 s …  3.605 s    10 runs

to

Benchmark #1: python3 test.py
  Time (mean ± σ):      3.393 s ±  0.040 s    [User: 3.552 s, System: 0.885 s]
  Range (min … max):    3.313 s …  3.438 s    10 runs