Make global scope enums accessible as types in GDScript

Add functions to CoreConstant so enums can be properly deduced. Also add
the enums in release builds to make consistent with ClassDB enums and
avoid differences in script compilation between debug and release.

modules/gdscript/tests/scripts/analyzer/warnings/cast_enum_bad_enum.out

@@ -2,5 +2,5 @@ GDTEST_OK
 >> WARNING
 >> Line: 5
 >> INT_AS_ENUM_WITHOUT_MATCH
->> Cannot cast 2 as Enum "cast_enum_bad_enum.gd::MyEnum": no enum member has matching value.
+>> Cannot cast 2 as Enum "cast_enum_bad_enum.gd.MyEnum": no enum member has matching value.
 2

modules/gdscript/tests/scripts/analyzer/warnings/cast_enum_bad_int.out

@@ -2,5 +2,5 @@ GDTEST_OK
 >> WARNING
 >> Line: 4
 >> INT_AS_ENUM_WITHOUT_MATCH
->> Cannot cast 2 as Enum "cast_enum_bad_int.gd::MyEnum": no enum member has matching value.
+>> Cannot cast 2 as Enum "cast_enum_bad_int.gd.MyEnum": no enum member has matching value.
 2