Add new DynamoSlider class.
Moved DynamoSlider to CoreNodesUI.
Move serialization shared logic into base class.
Hand-pick changes to slider classes and base class.
Remove dead IBlockingModel interface.
Fix two tests which referenced old Dynamo slider class.
Remove the old DynamoSlider class.
Remove two dead event handlers.
Rename to Number Slider and add search terms.
Rename double slider and add search terms.
Remove WindowsBase dependency.

Threading namespace is no longer needed. Remove WindowsBase reference
and cleanup unused using statements in several locations.
Visual tweaks to expander and slider.
Merge remote-tracking branch 'origin/master' into MAGN-5604

Conflicts:
	test/DynamoCoreUITests/NodeViewCustomizationTests.cs
Merge pull request #3404 from DynamoDS/MAGN-5604

MAGN-5604 Remove execution throttle.