fix(renderer): Interleave positive and negative feather atlas triangles (#11654) 37764336db

We were rendering the atlas with all negative triangles first, followed
by all positive triangles. This is the worst possible ordering for
maintaining high precision in a 16-bit coverage buffer, since as the
magnitude accumulates, we lose the lower bits. Instead, render the
positive/negative triangles interleaved, in the same order naturally
come in. This requires an extra check in the fragment shader for whether
the triangle is clockwise.

Author: csmartdalton

.rive_head

@@ -1 +1 @@
-aa788cab462e8de4438e619a4047c7e6e39fcabb
+37764336dbdb4b78d2be6842cd9cf34dacf996f1