Constant tensor constructor should be automatically recognized as symmetric

When a tensor is constructed with all entries the same, it should automatically be wrapped in a `SymmetricTensor` with all axes symmetric.
Example:
```
Y = we.zeros((n, n))     # Currently a SymmetricTensor with symmetric_axes=(0,1) (Correct)
Z = we.zeros((n, n, n))    # Currently a raw WhestArray (Incorrect, should be SymmetricTensor with symmetric_axes=(0,1,2))
```