Use trait collection to resolve border colors (facebook#32492)

Summary:
facebook@c974cbf changed the border colors to be of UIColor instead of CGColor. This allowed working with dark mode to switch the border colors automatically. However, in certain situation the system can't resolve the current trait collection (see https://stackoverflow.com/a/57177411/2525941). This commit resolves the colors with the current trait collection to ensure the right colors are selected. This matches with the behavior of how the background color is resolved (also in displayLayer:).

## Changelog

[iOS] [Fixed] - Resolve border platform color based on current trait collection

Pull Request resolved: facebook#32492

Test Plan: Same test plan as facebook#29728

Reviewed By: sammy-SC

Differential Revision: D33819225

Pulled By: cortinico

fbshipit-source-id: 2f8024be7ee7b32d1852373b47fa1437cc569391

React/Views/RCTView.m

@@ -1124,10 +1124,13 @@ - (RCTCornerRadii)cornerRadii
   };
 }
 
-- (RCTBorderColors)borderColors
+- (RCTBorderColors)borderColorsWithTraitCollection:(UITraitCollection *)traitCollection
 {
   const BOOL isRTL = _reactLayoutDirection == UIUserInterfaceLayoutDirectionRightToLeft;
 
+  UIColor *directionAwareBorderLeftColor = nil;
+  UIColor *directionAwareBorderRightColor = nil;
+
   if ([[RCTI18nUtil sharedInstance] doLeftAndRightSwapInRTL]) {
     RCTUIColor *borderStartColor = _borderStartColor ?: _borderLeftColor; // macOS RCTUIColor
     RCTUIColor *borderEndColor = _borderEndColor ?: _borderRightColor; // macOS RCTUIColor
@@ -1147,10 +1150,10 @@ - (RCTBorderColors)borderColors
   RCTUIColor *directionAwareBorderRightColor = isRTL ? _borderStartColor : _borderEndColor; // macOS RCTUIColor
 
   return (RCTBorderColors){
-    (_borderTopColor ?: _borderColor).CGColor,
-    (directionAwareBorderLeftColor ?: _borderLeftColor ?: _borderColor).CGColor,
-    (_borderBottomColor ?: _borderColor).CGColor,
-    (directionAwareBorderRightColor ?: _borderRightColor ?: _borderColor).CGColor,
+      (borderTopColor ?: borderColor).CGColor,
+      (directionAwareBorderLeftColor ?: borderColor).CGColor,
+      (borderBottomColor ?: borderColor).CGColor,
+      (directionAwareBorderRightColor ?: borderColor).CGColor,
   };
 }
 
@@ -1181,7 +1184,7 @@ - (void)displayLayer:(CALayer *)layer
 
   const RCTCornerRadii cornerRadii = [self cornerRadii];
   const UIEdgeInsets borderInsets = [self bordersAsInsets];
-  const RCTBorderColors borderColors = [self borderColors];
+  const RCTBorderColors borderColors = [self borderColorsWithTraitCollection:self.traitCollection];
 
   BOOL useIOSBorderRendering = RCTCornerRadiiAreEqual(cornerRadii) && RCTBorderInsetsAreEqual(borderInsets) &&
       RCTBorderColorsAreEqual(borderColors) && _borderStyle == RCTBorderStyleSolid &&