use UOp.shape property instead of UOp.st (#12664)

* work on shape property

* reshape causing issues

* more mops

* all mops

* need to cache it

* _shape is like _device

* mostly works

* shape is good

* const uses _shape

* fix tests

* size doesn't use st

* close

* test is broken

* one less st

* hack for 3 op assign

* oops, i didn't mean to change that

* support emulate in the NullDevice

* reproed failure in emulation

* fix wmma

test/test_multitensor.py

@@ -658,7 +658,7 @@ class TestMultiTensor(unittest.TestCase):
 
   # it doesn't work like this anymore
   # NOTE: this never failed in assign_multi, it failed tensor spec because MULTI was never pushed in the graph
-  @unittest.expectedFailure
+  @unittest.skip("this test is broken")
   def test_mlb_assign_change_axis(self):
     t_none = Tensor.zeros((16, 16)).shard(devices_2).contiguous().realize()
     t_zero = Tensor.ones((16, 16)).shard(devices_2, axis=0)