gh-110850: Cleanup pycore_time.h includes (#115724)

<pycore_time.h> include is no longer needed to get the PyTime_t type
in internal header files. This type is now provided by <Python.h>
include. Add <pycore_time.h> includes to C files instead.

Python/gc.c

@@ -12,6 +12,7 @@
 #include "pycore_object_alloc.h"  // _PyObject_MallocWithType()
 #include "pycore_pyerrors.h"
 #include "pycore_pystate.h"       // _PyThreadState_GET()
+#include "pycore_time.h"          // _PyTime_GetPerfCounter()
 #include "pycore_weakref.h"       // _PyWeakref_ClearRef()
 #include "pydtrace.h"