[dartpy] Fix enabling drag and drop of InteractiveFrame

[jslee02]

Enabling drag and drop for InteractiveFrame currently doesn't work as expected because of the order of Python bindings for dart::gui::osg::Viewer::enableDragAndDrop(...). pybind11 calls earlier-defined overloads. For InteractiveFrame case, enableDragAndDrop(Entity*) is called instead of enableDragAndDrop(InteractiveFrame*) because enableDragAndDrop(Entity*) is defined in prior to the other (and it's compatible since Entity is a base of InteractiveFrame). To prevent this, this PR defines enableDragAndDrop(InteractiveFrame*) (and other functions overloaded for derived classes of Entity) before enableDragAndDrop(Entity*).

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[codecov]

Codecov Report

Merging #1432 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1432      +/-   ##
==========================================
- Coverage      58%   57.99%   -0.02%     
==========================================
  Files         412      412              
  Lines       29861    29861              
==========================================
- Hits        17322    17319       -3     
- Misses      12539    12542       +3

Impacted Files	Coverage Δ
dart/dynamics/Skeleton.cpp	66.16% <0%> (-0.17%)	⬇️