[Mosaic:TPU] Roll forward of cl/708011538 (expanded trunc support), minus changes in infer-vector-layout
We can enable them later but at least this way the support is available to build on
(e.g. in the new insert relayouts pass)
Reverts 05f3a701e769748ff1ec51d50324a3595c4aff0d
PiperOrigin-RevId: 708397219