Read catalog - get only positional coordinates by default

[nevencaplar]

Feature request

When reading a catalog with read_hipscat change the default to only read in ra, dec coordinates, i.e., spatial coordinates, and require user to specify further columns. This is to avoid extensive loading when exploring the datasets (e.g., loading 10, 20, 50 columns of a catalog when only looking at the number of objects or similar).

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• I have described the purpose of the suggested change, specifying what I need the enhancement to accomplish, i.e. what problem it solves.
• I have included any relevant links, screenshots, environment information, and data relevant to implementing the requested feature, as well as pseudocode for how I want to access the new functionality.
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[hombit]

Theoretically dask-expr would allow us to load only those columns we actually use, but it would require to change some LSDB code, for at least 1) data loading, and 2) cross-matching.

[nevencaplar]

@dougbrn Can you please link here the presentation that you did which showed that dask-expr is pretty limited in that regard. or was it your @hombit presentation?

[delucchi-cmu]

STSci requested a default_columns kind of attribute, to accomplish a similar goal, but potentially with a few more columns (e.g. redshift and r_mag).

See astronomy-commons/hats#322

[nevencaplar]

Connected with: #529