gg: add draw_ellipse_filled() + draw_ellipse_empty() APIs (#12869)

vlib/gg/draw_fns_api_test.v

@@ -0,0 +1,24 @@
+import os
+
+fn test_all_samples_can_be_compiled() {
+	vexe := @VEXE
+	vroot := os.dir(vexe)
+	samples := os.walk_ext('$vroot/vlib/gg/testdata', '.vv')
+	mut fails := []string{}
+	for program_source in samples {
+		compile_cmd := '"$vexe" "$program_source"'
+		res := os.execute(compile_cmd)
+		if res.exit_code != 0 {
+			eprintln('>>> FAIL $compile_cmd')
+			fails << compile_cmd
+		}
+		println('OK $compile_cmd')
+	}
+	if fails.len > 0 {
+		eprintln('> Failed summary:')
+		for f in fails {
+			eprintln('   failed cmd: $f')
+		}
+		assert false
+	}
+}