Move the esmvalcore.local and esmvalcore.esgf modules into the esmvalcore.io module

[bouweandela]

Description

Move the esmvalcore.local and esmvalcore.esgf modules into the esmvalcore.io module so we have all data sources in one place.

• Importing esmvalcore.local is deprecated and will be removed in v2.16. It can be imported as esmvalcore.io.local instead.
• Importing esmvalcore.esgf is deprecated and will be removed in v2.16. It can be imported as esmvalcore.io.esgf instead.

Links to documentation:

• https://esmvaltool--2911.org.readthedocs.build/projects/ESMValCore/en/2911/api/esmvalcore.io.html
• https://esmvaltool--2911.org.readthedocs.build/projects/ESMValCore/en/2911/api/esmvalcore.local.html
• https://esmvaltool--2911.org.readthedocs.build/projects/ESMValCore/en/2911/api/esmvalcore.esgf.html

Closes #2882

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.57%. Comparing base (5a317f5) to head (afc9b1b).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2911      +/-   ##
==========================================
+ Coverage   95.55%   95.57%   +0.02%     
==========================================
  Files         263      266       +3     
  Lines       15506    15520      +14     
==========================================
+ Hits        14817    14834      +17     
+ Misses        689      686       -3     

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[valeriupredoi]

much appreciated, bud 🍺

[bouweandela]

Thanks for reviewing V!