Prevent useless `DimShuffle`s produced by `TensorVariable.dimshuffle`

[brandonwillard]

The DimShuffle in the following should not be produced:

import aesara
import aesara.tensor as at


x = at.scalar("x")
z = x.dimshuffle()

aesara.dprint(z)
# InplaceDimShuffle{} [id A]
#  |x [id B]