Features:
* Scales dash spacing with border width.
* Laying out dashes around rounded corners.
* Varying border widths with rounded corners - now uses an ellipse for the inner edge of the border.
* When there are no rounded corners, each straight border is laid out separately, so that the dashes to meet at the corners.
* All sides of each dash are antialiased.


Release Notes:
- N/A
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Co-authored-by: Michael Sloan <michael@zed.dev>
Co-authored-by: Ben <ben@zed.dev>