`YGFloatOptional`: Move binary operators to free functions
`YGFloatOptional`: Move binary operators to free functions

Summary:
@public

Having binary operators as member functions has disadvantages:

- the left hand side cannot be converted to `YGFloatOptional` implicitly (which we need for `YGStyle` refs)
- Operators are not necessarily commutative.

By moving these operators into free functions, and adding overloads for both variants if one operand is `float`, we get these properties.

Reviewed By: SidharthGuglani

Differential Revision: D15078962

fbshipit-source-id: 2e228a2ef90a8083c91788caa9eedfd4d140677f

exponentjs/react-native,hoangpham95/react-native,arthuralee/react-native,exponent/react-native,myntra/react-native,janicduplessis/react-native,arthuralee/react-native,facebook/react-native,hoangpham95/react-native,pandiaraj44/react-native,hoangpham95/react-native,janicduplessis/react-native,hammerandchisel/react-native,facebook/react-native,hammerandchisel/react-native,myntra/react-native,pandiaraj44/react-native,pandiaraj44/react-native,arthuralee/react-native,myntra/react-native,facebook/react-native,hammerandchisel/react-native,myntra/react-native,hoangpham95/react-native,janicduplessis/react-native,exponent/react-native,javache/react-native,javache/react-native,facebook/react-native,exponent/react-native,pandiaraj44/react-native,exponentjs/react-native,facebook/react-native,myntra/react-native,exponentjs/react-native,janicduplessis/react-native,hammerandchisel/react-native,janicduplessis/react-native,myntra/react-native,exponentjs/react-native,hammerandchisel/react-native,exponent/react-native,arthuralee/react-native,pandiaraj44/react-native,exponentjs/react-native,exponent/react-native,facebook/react-native,hoangpham95/react-native,hammerandchisel/react-native,exponentjs/react-native,hammerandchisel/react-native,exponentjs/react-native,javache/react-native,exponent/react-native,exponentjs/react-native,hoangpham95/react-native,exponent/react-native,pandiaraj44/react-native,janicduplessis/react-native,javache/react-native,javache/react-native,pandiaraj44/react-native,javache/react-native,javache/react-native,facebook/react-native,exponent/react-native,facebook/react-native,myntra/react-native,javache/react-native,hammerandchisel/react-native,pandiaraj44/react-native,hoangpham95/react-native,hoangpham95/react-native,myntra/react-native,arthuralee/react-native,janicduplessis/react-native,janicduplessis/react-native,myntra/react-native,javache/react-native,facebook/react-native