Depth raster: Stop a row once it has left the triangle

The triangle is convex, so once a row has been entered and left, the
rest of it is outside. This cut cycles by 5% in Wipeout Pure, where depth
raster is on for the lens flares.

The test checks the covered pixels against a per-pixel edge test.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

unittest/UnitTest.cpp

@@ -3104,6 +3104,7 @@ bool TestMpegCsc();
 bool TestSplineTessellation();
 bool TestGEMath();
 bool TestBoundingBoxFast();
+bool TestDepthRaster();
 bool TestDemangle();
 
 // The 8.3 short names games read out of d_private. These aren't verified against hardware yet (no
@@ -3432,6 +3433,7 @@ TestItem availableTests[] = {
 #endif
 	TEST_ITEM(VertexJit),
 	TEST_ITEM(BoundingBoxFast),
+	TEST_ITEM(DepthRaster),
 	TEST_ITEM(VFPUSinCos),
 	TEST_ITEM(VFPUDot),
 	TEST_ITEM(MathUtil),