Refactor ArraySubset iterators

[LDeakin]

This ArraySubset iterator refactor uncouples iterator lifetimes from the array subset and adds parallel iterator support (into_par_iter()) for some iterators. Downstream users doing array subset iteration will need to adjust calls from

array_subset.iter_<variant>(...)

to

array_subset.<variant>(...).into_iter()

[codecov]

Codecov Report

Attention: 121 lines in your changes are missing coverage. Please review.

Comparison is base (8d5a27c) 75.70% compared to head (b1be44a) 75.76%.

Files	Patch %	Lines
src/array/array_async_readable.rs	0.00%	30 Missing ⚠️
src/array/array_async_writable.rs	0.00%	20 Missing ⚠️
src/array_subset/iterators/indices_iterator.rs	88.72%	15 Missing ⚠️
src/array_subset/iterators/chunks_iterator.rs	90.17%	11 Missing ⚠️
src/array/array_async_readable_writable.rs	0.00%	8 Missing ⚠️
...ay_subset/iterators/contiguous_indices_iterator.rs	50.00%	8 Missing ⚠️
...terators/contiguous_linearised_indices_iterator.rs	77.77%	8 Missing ⚠️
...ay_subset/iterators/linearised_indices_iterator.rs	81.39%	8 Missing ⚠️
src/array/array_sync_writable.rs	0.00%	5 Missing ⚠️
src/array/array_sync_readable.rs	66.66%	4 Missing ⚠️
... and 2 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #7      +/-   ##
==========================================
+ Coverage   75.70%   75.76%   +0.06%     
==========================================
  Files         124      124              
  Lines       17878    18084     +206     
==========================================
+ Hits        13535    13702     +167     
- Misses       4343     4382      +39     

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