Enhance Wind/3Dp data handling

[jgieseler]

• Fall back to CDAWEb for downloading if https://sprg.ssl.berkeley.edu is failing
• Add support for datasets 'WI_ELSP_3DP', 'WI_ELPD_3DP', 'WI_EHSP_3DP', and 'WI_EHPD_3DP'

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 4 lines in your changes missing coverage. Please review.

Project coverage is 75.53%. Comparing base (edceff4) to head (30860db).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
seppy/loader/wind.py	66.66%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #67      +/-   ##
==========================================
+ Coverage   75.41%   75.53%   +0.11%     
==========================================
  Files          11       11              
  Lines        2331     2342      +11     
==========================================
+ Hits         1758     1769      +11     
  Misses        573      573              

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