Fix multi-line comments for cpp enums (#5345) (#5346)

- fix CSharp comments generation
- fix Python comments generation
- fix Lua comments generation
- fix PHP comments generation
- fix Dart comments generation
- add brief description of Color enum
- add multi-line comments to the Monster:Color

tests/monster_test.fbs

@@ -14,7 +14,15 @@ namespace MyGame.Example;
 
 attribute "priority";
 
-enum Color:ubyte (bit_flags) { Red = 0, Green, Blue = 3, }
+/// Composite components of Monster color.
+enum Color:ubyte (bit_flags) { 
+  Red = 0, // color Red = (1u << 0)
+  /// \brief color Green
+  /// Green is bit_flag with value (1u << 1)
+  Green, 
+  /// \brief color Blue (1u << 3)
+  Blue = 3, 
+}
 
 union Any { Monster, TestSimpleTableWithEnum, MyGame.Example2.Monster }