Previously KeyList constants came from the GlobalConstants.hpp header,
but this did not work when compiling for HTML5. Therefore, we now get
the globals constants from the GDNative API.
Throws the error:
`LNK2019: unresolved external symbol godot_get_global_constants referenced in function "private: static void __cdecl godot::Terminal::_populate_key_list(void)" (?_populate_key_list@Terminal@godot@@CAXXZ)`
in GitHub Windows action. So use the old technique on Windows for now.
This is a prerequisite for HTML5 support.
