Fix Bug #66622: Closures do not correctly capture the late bound class (static::) in some cases

This PR fixes bug 66622. It does three things:

 - Moves `Zend/tests/closure_*.phpt` to `Zend/tests/closure/*.phpt`. I was running these tests a lot and didn't have time to run the full `Zend/tests` suite. Some minor cleanup associated with the file renaming.
 - Fixes static closures to use late static binding
 - Automatically promotes non-static closures to be static when defined in a static method.