all: Use mp_obj_malloc everywhere it's applicable.

This replaces occurences of

    foo_t *foo = m_new_obj(foo_t);
    foo->base.type = &foo_type;

with

    foo_t *foo = mp_obj_malloc(foo_t, &foo_type);

Excludes any places where base is a sub-field or when new0/memset is used.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

extmod/machine_signal.c

@@ -108,8 +108,7 @@ STATIC mp_obj_t signal_make_new(const mp_obj_type_t *type, size_t n_args, size_t
         }
     }
 
-    machine_signal_t *o = m_new_obj(machine_signal_t);
-    o->base.type = type;
+    machine_signal_t *o = mp_obj_malloc(machine_signal_t, type);
     o->pin = pin;
     o->invert = invert;
     return MP_OBJ_FROM_PTR(o);