Update Catalog Lazy Representation

[smcguire-cmu]

• Changes index column from healpix_29 divisions to healpix pixels
• Adds warning that catalog is only lazily read

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 2 lines in your changes missing coverage. Please review.

Please upload report for BASE (margin@8269182). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/lsdb/catalog/dataset/dataset.py	75.00%	1 Missing ⚠️
src/lsdb/catalog/dataset/healpix_dataset.py	92.85%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             margin     #514   +/-   ##
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  Coverage          ?   97.47%           
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  Files             ?       41           
  Lines             ?     1626           
  Branches          ?        0           
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  Hits              ?     1585           
  Misses            ?       41           
  Partials          ?        0           

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[camposandro]

Awesome, looks great! Can we just update the images of the Getting Started docs to show the current representation? the second image is unrelated to this change but it still shows a _hipscat_index column.