perf(draw) reimplement circle drawing algorithms (#2374)

* perf(draw) reimplement circle drawing algorithms

Imporve the speed of circle drawing
Add circle draw caching
Various other speed improvements

* docs describe how to use masks

* fix(draw) add missing GC root usage

src/lv_conf_internal.h

@@ -250,6 +250,19 @@
 #    define  LV_SHADOW_CACHE_SIZE    0
 #  endif
 #endif
+
+/* Set number of maximally cached circle data.
+ * The circumference of 1/4 circle are saved for anti-aliasing
+ * radius * 4 bytes are used per circle (the most often used radiuses are saved)
+ * 0: to disable caching */
+#ifndef LV_CIRCLE_CACHE_SIZE
+#  ifdef CONFIG_LV_CIRCLE_CACHE_SIZE
+#    define LV_CIRCLE_CACHE_SIZE CONFIG_LV_CIRCLE_CACHE_SIZE
+#  else
+#    define  LV_CIRCLE_CACHE_SIZE    4
+#  endif
+#endif
+
 #endif /*LV_DRAW_COMPLEX*/
 
 /*Default image cache size. Image caching keeps the images opened.