bpo-45963: Make space for the InterpreterFrame of a generator in that generator. (GH-29891)

* Make generator, coroutine and async gen structs all the same size.

* Store interpreter frame in generator (and coroutine). Reduces the number of allocations neeeded for a generator from two to one.

Lib/test/test_sys.py

@@ -1340,7 +1340,7 @@ class SizeofTest(unittest.TestCase):
             check(bar, size('PP'))
         # generator
         def get_gen(): yield 1
-        check(get_gen(), size('P2PPP4P'))
+        check(get_gen(), size('P2PPP4P4c8P2iciP'))
         # iterator
         check(iter('abc'), size('lP'))
         # callable-iterator