[Mosaic:TPU] Get rid of RectangularVregBounds and clean up VectorLayout::tileDataBounds
Also fixes a bug in in the vector.multi_reduction rule where replicated offsets were being checked against non-implicit dimensions instead of implicit ones. This was being hidden by hitting "Not implemented" when having implicit dimensions and replicated offsets in tileDataBounds
PiperOrigin-RevId: 794438166