Make Monster's Color unsigned (#5318)

- update C++ monster_test::Color to unsigned type
- update Go Color:ubyte in the go_test.go
- add workaround for unsigned enum in java test
- sync generate.bat and generate.sh

tests/monster_test.fbs

@@ -14,7 +14,7 @@ namespace MyGame.Example;
 
 attribute "priority";
 
-enum Color:byte (bit_flags) { Red = 0, Green, Blue = 3, }
+enum Color:ubyte (bit_flags) { Red = 0, Green, Blue = 3, }
 
 union Any { Monster, TestSimpleTableWithEnum, MyGame.Example2.Monster }