Add xcDeferFulfillment to help with tests that have publishers. (#1278)

* Add xcAwaitDeferred to aid with tests that have publishers.

* Improve naming

* Address Comments

- Fix naming
- Add optional expectation message
- Use trailing closure syntax

ElementX/Sources/Other/SwiftUI/Views/RoundedCornerShape.swift

@@ -20,11 +20,6 @@ struct RoundedCornerShape: Shape {
     let radius: CGFloat
     let corners: UIRectCorner
 
-    init(radius: CGFloat, corners: UIRectCorner) {
-        self.radius = radius
-        self.corners = corners
-    }
-
     func path(in rect: CGRect) -> Path {
         var path = Path()