Add CatalogIterator Interface

[dougbrn]

Closes #1042. Generally pretty open on a lot of the design decisions, naming, etc here. I didn't attempt the pytorch integration mentioned in the issue, happy to discuss more about that!

[codecov]

Codecov Report

❌ Patch coverage is 98.21429% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 96.69%. Comparing base (b1f2780) to head (56d6084).

Files with missing lines	Patch %	Lines
src/lsdb/iterator/catalog_iterator.py	98.18%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1246      +/-   ##
==========================================
+ Coverage   96.66%   96.69%   +0.02%     
==========================================
  Files          46       47       +1     
  Lines        2877     2933      +56     
==========================================
+ Hits         2781     2836      +55     
- Misses         96       97       +1     

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[github-actions]

Before [b1f2780]	After [fd12ad4]	Ratio	Benchmark (Parameter)
8.10±0.1s	8.28±0.02s	1.02	benchmarks.time_lazy_crossmatch_many_columns_all_suffixes
175±1ms	177±0.9ms	1.01	benchmarks.time_open_many_columns_list
50.2±0.4ms	50.8±0.8ms	1.01	benchmarks.time_polygon_search
7.08±0.07s	7.08±0.01s	1	benchmarks.time_create_large_catalog
1.06±0.01s	1.06±0.01s	1	benchmarks.time_create_midsize_catalog
109±2ms	109±1ms	1	benchmarks.time_kdtree_crossmatch
3.88±0.03s	3.87±0.01s	1	benchmarks.time_open_many_columns_all
388±3ms	386±2ms	0.99	benchmarks.time_open_many_columns_default
19.9±0.02s	19.8±0.07s	0.99	benchmarks.time_save_big_catalog
30.4±0.7ms	29.7±0.2ms	0.98	benchmarks.time_box_filter_on_partition

Click here to view all benchmarks.