ENH: adding Irsa.list_columns

[bsipocz]

to list the columns of a given catalog.

I've done it to be similar to list_catalogs, and return a dict of name: description pairs rather than a table with two columns, but I'm happy to change it to return a table instead. (but then we should probably do the same for list_catalogs, too)

The obvious advantage I see for the dict approach is then there is no default ellipsis added, all the columns are listed out on the screen.

This is to close #3177

I'm adding docs and tests while waiting for the review.

[codecov]

Codecov Report

Attention: Patch coverage is 30.00000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 69.05%. Comparing base (44b034a) to head (d677fa1).
Report is 17 commits behind head on main.

Files with missing lines	Patch %	Lines
astroquery/ipac/irsa/core.py	30.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3265      +/-   ##
==========================================
- Coverage   69.08%   69.05%   -0.04%     
==========================================
  Files         232      232              
  Lines       19639    19652      +13     
==========================================
+ Hits        13568    13570       +2     
- Misses       6071     6082      +11     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.