GAIA: new simplified cross match method

[cosmoJFH]

Dear astroquery team,

The current implementation of the astroquery.gaia built-in cross-match tool relies in a sub-optimal intermediate ADQL query. Furthermore (and after uploading a table to the user space), it requires a 3-step approach involving different functionalities (each of them requiring multiple "user clicks"):

1. Update the user table metadata to flag the positional (ra & dec) fields using a dedicated method ("update_user_table" - see Sect 2.5 in the astroquery.gaia documentation)
2. Launch the built-in cross-match method ("cross_match" - see Sect 2.6 in the astroquery.gaia documentation)
3. Launch a sub-optimal and complicated ADQL query using the "launch_job" or "launch_job_async" method (see Sect 2.6 in the astroquery.gaia documentation).

We propose to streamline this procedure to improve the user experience and hopefully promote the usage of this functionality by updating the current implementation.

The proposed mechanism:

1. allows to obtain a basic cross-match using a single step (versus three steps currently).
2. allows to perform cross-matches between: user_table X user_table, user_table X GACS_table, and GACS_table X GACS_table (as in the current implementation).

We have developed the new method cross_match_basic as well as new tests. This change is backward compatible with the present implementation of the cross-match method.

cc @esdc-esac-esa-int

jira: GAIASWRQ-25

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.97%. Comparing base (823e49f) to head (e63ae6b).
Report is 16 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3320      +/-   ##
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+ Coverage   69.88%   69.97%   +0.08%     
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  Files         232      232              
  Lines       19761    19814      +53     
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+ Hits        13810    13864      +54     
+ Misses       5951     5950       -1     

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