Remove the Variant shape function registry and all references.

Variant shape information is now stored in the HandleData.shape_and_type
during shape inference.

While we're at it, propagate DT_VARIANT ShapeAndType handles through
a number of ops ("AddN", "ZerosLike", and several resource variable ops).

For DT_VARIANT types stored inside a ResourceVariable, the ResourceVariable's
ShapeAndType array is extended.  Before it had one entry storing the dtype and
shape of the tensor stored inside the Variable.  Now, entries indexed 1,... will
contain the ShapeAndType data read from the DT_VARIANT passed as the initializer
at Variable creation time.  ResourceVariable read ops will propagate this
information back out by reading ShapeAndType[1:] from the resource tensor's
handle data.

PiperOrigin-RevId: 231057278