Context:
The dtype for qml.sample(Identity(0)) doesn't match the dtype for its eigvals, and it breaks JAX-JIT. Some observables use int, some use float, depending on the dtype of eigvals. We're opting to standardize this to be floats.

Description of the Change:
Change eigvals of X, Y, Z and Hadamard to be floats. This will also affect Tensor, which previously was int if it was composed only of those observables.

The generation of samples is modified in _qubit_device and on SampleMP, because it wasn't actually using the eigvals for these 4 operators.

Benefits:
We can do this:

@qml.qnode(qml.device('default.qubit', shots=50))
def circuit(x):
    qml.RX(x, wires=0)
    return qml.sample(op=qml.I(0))
    
jax.jit(circuit)(jax.numpy.array(0.5))

and we are less likely to have similar/related bugs in the future.

Possible Drawbacks:
Samples that used to be int will become float

Related GitHub Issues:
#5369