Recent update breaks mirgecom

[MTCam]

This update appears to break TPE in mirgecom.
4cb7c84

Now, use of TPE in mirgecom gets this error:

                # FIXME: can be gotten rid of by updating meshmode operators
>               basis_1d = out_grp.bases_1d()
E               AttributeError: 'LegendreGaussLobattoTensorProductElementGroup' object has no attribute 'bases_1d'
grudge/grudge/op.py:766: AttributeError

It was not entirely clear to me how to fix up our grudge/op to be compatible with this change.

[inducer]

See @a-alveyblanc's comment on #409.