Fix bug with borderRadii caused by iOS 10 specific code

Summary:
Non-uniform edge insets caused issues on iOS 10. The code nowadays interferes with the rendering for large borderRadii so this diff removes it.

Since we didn't support this behavior before there are some bugs/missing features that happen:

T186810893 Incorrect border rendering with large radii
T186812303 View discoloring with overlapping border radii
T186812736 Add support for vertical and horizontal border radii

## Changelog:

[iOS][Fixed] - Removed Legacy iOS 10 code messing with border radius

Reviewed By: NickGerleman

Differential Revision: D56333637

fbshipit-source-id: 92b1bb1459d1e95476b3d768db725dfbbc1e55ae