Add missing test for encode_utf8 (#683)

* Add missing test for encode_utf8

* Fix CI error by only run under std

* Merge test into testing framework for utf8 testing

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Co-authored-by: cxworks <cxworks@qq.com>

tests/basic_types.rs

@@ -33,7 +33,7 @@ fn test_numbers() {
     the_same(false);
 
     // utf8 characters
-    for char in "aÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö文".chars()
+    for char in "aÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö文😀😁😂😃".chars()
     {
         the_same(char);
     }