Add `replace!` function for replacing a `Tensor` from a `TensorNetwork`

[jofrevalles]

Summary

Add a replace! function that allows users to replace a specific Tensor within a TensorNetwork. The function should ensure that the new Tensor maintains the same connections with respect to the labels as the original Tensor.

The replace! function should have the following input parameters and expected behavior:

• Input: TensorNetwork, index of the Tensor to be replaced, new Tensor
• Output: Updated TensorNetwork with the specified Tensor replaced
• Checks: Verify that the new Tensor is compatible with the existing TensorNetwork, maintaining the same label connections

Example

function replace!(state::TensorNetwork, index::Int, new_tensor::Tensor)
    # Perform checks and update the state
    ...
end