Enable runtime_validation package/module-wide

[smarie]

It would be very practical to be able to enforce PEP484 type validation package/module-wide, typically when the package/module developer thinks it should be enforced for his package/module to work properly.

In this case he could write something in his __init__ file (for packages), or at the end of his python file (for modules), to automatically decorate all symbols of the package/module with PEP484 type validation.