Einsum fails with repeated inputs

[ricardoV94]

Description

import pytensor.tensor as pt

x = pt.matrix("x")
pt.einsum("ij,ij->i", x, x.copy())  # Fine
pt.einsum("ij,ij->i", x, x)  # Raises

ValueError: The following variables were provided more than once as inputs to the OpFromGraph, resulting in an invalid graph: [x]. Use dummy variables or var.copy() to distinguish variables when creating the OpFromGraph graph.

We should add an x.copy() internally, since this is an implementation detail