Add mem_size histogram support to generate_alignment

[olivialynn]

Change Description

Along with astronomy-commons/hats-import#631, this will close astronomy-commons/hats-import#449.

• First PR: change the directory names to mem_size_histogram and row_count_histogram
  • Rename histogram directory (histograms/ -> row_count_histograms/) hats-import#602
• Second PR: create the mem_size_histogram (but don't do anything with it)
  • Add mem_size histogram hats-import#619
• Third PR: use the mem_size_histogram to do the partitioning
  • 📍You are here (and the hats-import part of this is here)

Solution Description

• Alignment files traditionally include tuples of length 3: (order, pixel, row_count).
• This change extends them to (optionally) have an additional element: (order, pixel, mem_size, row_count), which is used for partitioning logic when partitioning by memory size.
• We preserve data about the row_count of each pixel in the alignment file, as this allows us to quickly guarantee that all rows have been accounted for throughout the various stages of the pipeline.

[github-actions]

Before [53a04bc]	After [f1d5d29]	Ratio	Benchmark (Parameter)
12.4±0.4ms	12.8±0.5ms	1.03	benchmarks.Suite.time_inner_pixel_alignment
353±2ms	352±1ms	1	benchmarks.Suite.time_outer_pixel_alignment
105±0.4ms	105±0.4ms	1	benchmarks.time_test_alignment_even_sky
1.04±0.03ms	1.05±0.03ms	1	benchmarks.time_test_cone_filter_multiple_order
36.3±0.6ms	36.0±0.2ms	0.99	benchmarks.Suite.time_pixel_tree_creation
226±3ms	224±0.8ms	0.99	benchmarks.time_open_large_catalog
36.4±0.09ms	35.9±0.2ms	0.99	benchmarks.time_open_midsize_catalog
227±0.9ms	226±2ms	0.99	benchmarks.time_small_cone_large_catalog

Click here to view all benchmarks.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.89%. Comparing base (53a04bc) to head (9ac5477).
⚠️ Report is 71 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #599      +/-   ##
==========================================
+ Coverage   92.83%   92.89%   +0.06%     
==========================================
  Files          49       49              
  Lines        2234     2253      +19     
==========================================
+ Hits         2074     2093      +19     
  Misses        160      160              

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[delucchi-cmu]

This looks good so far - just the remaining comment about 4-tuple -> 3-tuple