Improve load

[henry2004y]

• Refactor IDL data loading
• Refactor load by removing list conversion
• Add iFile keyword to load for IDL file selection

[codecov]

Codecov Report

Attention: Patch coverage is 75.86207% with 7 lines in your changes missing coverage. Please review.

Project coverage is 55.56%. Comparing base (e3c1564) to head (f371216).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/flekspy/idl/idl.py	64.70%	6 Missing ⚠️
src/flekspy/__init__.py	91.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #35      +/-   ##
==========================================
+ Coverage   55.32%   55.56%   +0.23%     
==========================================
  Files          12       12              
  Lines        1728     1726       -2     
==========================================
+ Hits          956      959       +3     
+ Misses        772      767       -5     

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