rust-cpython: move py_shared_state to PySharedRefCell object
The goal of this series is to encapsulate more "py_shared" thingy and
reduce the size of the macro, which is hard to debug.
Since py_shared_state manages the borrowing state of the object owned by
PySharedRefCell, this change makes more sense. If a PyObject has more than
one data to be leaked into Python world, each PySharedState should incref
the parent PyObject, and keep track of the corresponding borrowing state.
{
// Enforcing
"eqeqeq" : true, // true: Require triple equals (===) for comparison
"forin" : true, // true: Require filtering for..in loops with obj.hasOwnProperty()
"freeze" : true, // true: prohibits overwriting prototypes of native objects such as Array, Date etc.
"nonbsp" : true, // true: Prohibit "non-breaking whitespace" characters.
"undef" : true, // true: Require all non-global variables to be declared (prevents global leaks)
// Environments
"browser" : true // Web Browser (window, document, etc)
}