Rework component_pool chunk storage

[kgorking]

Use something like a sparse_set to manage the chunk storage. Keep them ordered, without the need to move them around too much (swap-from-last erases ok).

[kgorking]

Reason:

• The current implementation was a fun experiment, but it has gotten unwieldy and hard to maintain.

References:

• Array layouts for comparison-based searching
• AA tree
• AA tree paper: Balanced search trees made simple
• Join-based tree algorithms

Plan:

• Create a self-contained range tree that can hold ranges and their data
  • Implement as an AA tree
  • Use a compact layout. New data is filled into current holes or appended to the end.
• Write algo for tree diff/intersection

[kgorking]

Well nuts to that. Wrote an allocator instead.