Refactor VectorField() function

[Sichao25]

• Optimized the usage of SvcVectorField class in VectorField() function.
• Created several helper functions to increase the readability of VectorField().
• Remove the dynode_old method.
• Moved VectorField() to a separate file VectorField.py.
• Renamed VectorField2D/VectorField3D to Topography2D/Topography3D.

[codecov-commenter]

Codecov Report

Attention: 88 lines in your changes are missing coverage. Please review.

Comparison is base (e87f702) 22.17% compared to head (5d704e6) 22.27%.

Files	Patch %	Lines
dynamo/vectorfield/VectorField.py	56.99%	83 Missing ⚠️
dynamo/plot/topography.py	25.00%	3 Missing ⚠️
dynamo/vectorfield/topography.py	50.00%	2 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #620      +/-   ##
==========================================
+ Coverage   22.17%   22.27%   +0.10%     
==========================================
  Files         166      167       +1     
  Lines       28032    28045      +13     
==========================================
+ Hits         6215     6248      +33     
+ Misses      21817    21797      -20     

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[Xiaojieqiu]

@Sichao25 can you please fix this conflict?