[Bug] AmbiguousLookupError for dot with Identity

[f0uriest]

🐛 Bug

multiplying a dense or diagonal matrix by an Indentity matrix gives a dispatch failure:

import cola
import jax.numpy as jnp
A = cola.ops.Dense(jnp.diag(jnp.arange(4)))
B = cola.ops.I_like(A)
A@B

** Stack trace/error message **

AmbiguousLookupError: For function `dot`, `(<4x4 Dense with dtype=int64>, <4x4 Identity with dtype=int64>)` is ambiguous among the following:
  Dispatched on dot(cola.ops.operator_base.LinearOperator, cola.ops.operator_base.LinearOperator) (precedence: 0)
  Dispatched on dot(typing.Any, cola.ops.operators.Identity) (precedence: 0)```