wg/gl_engine: standardize shapes closing precision

The sw_engine, when determining the outline, converts
floats to ints by multiplying them x64, resulting in
a comparison precision of 1/64 = 0.015625.
Both gl_engine and wg_engine operate on floats. Before
adding a closing point to a shape, they performed a comparison
to check if the point differed from the starting point:
- wg: with a precision of 1e-3 (using length2, i.e., eps = 1e-6
- gl: used direct == comparison.
Now, consistency has been ensured by introducing a comparison
precision of 1/64 in both wg_engine and gl_engine.

@issue: https://github.com/thorvg/thorvg/issues/2799
@issue: https://github.com/thorvg/thorvg/issues/3235

src/renderer/gl_engine/tvgGlTessellator.cpp

@@ -1746,7 +1746,7 @@ void Stroker::strokeCubicTo(const Point& cnt1, const Point& cnt2, const Point& e
 
 void Stroker::strokeClose()
 {
-    if (mStrokeState.prevPt != mStrokeState.firstPt) {
+    if (length(mStrokeState.prevPt - mStrokeState.firstPt) > 0.015625f) {
         this->strokeLineTo(mStrokeState.firstPt);
     }
 

src/renderer/wg_engine/tvgWgGeometry.h

@@ -148,7 +148,7 @@ struct WgVertexBuffer
     void close()
     {
         // check if last point is not to close to the first point
-        if (!tvg::zero(length2(data[0] - last()))) {
+        if (length(data[0] - last()) > 0.015625f) {
             append(data[0]);
         }
         closed = true;