Fix in TryGetBoundaryRectanglePoints after teleport

[keveleigh]

Overview

After a teleport, the boundary APIs still return positions around the origin, as though the camera has not moved.

I previously updated the RectangleParams method, but did not transform the RectanglePoints method. This fixes that.

Changes

• Related to Add inscribed rectangle to BoundaryManager #2403

[StephenHodgson]

Does this need to get ported into vNEXT?

[keveleigh]

@StephenHodgson
@davidkline-ms and I made sure it was accounted for in #2469 (this method ended up not existing there as written here, so we're good).