unit props deprecation: update proptypes and interfaces + all loaders

[davidhu2000]

• deprecate sizeUnit, heightUnit, widthUnit, and radiusUnit from proptypes and interfaces. The size, height, width, radius, and margin prop all accept number or string and will add px as a default, keep the original input as is if string with valid unit, or default to px with a console warning.
• changed css prop default to "" to fix typescript error for {} is not PrecompiledCss
• updated all tests to include test cases for number, string w/ valid unit, string w/ invalid unit