[XLA:CPU] Remove code from parallel CPU backend outlining that was causing...

[XLA:CPU] Remove code from parallel CPU backend outlining that was causing unnecessary copies to be inserted, and which is no longer necessary since we added co-located buffer support for kCall.
*) All bitcast copy is no longer necessary as CopyInsertion will insert copies
at the root of the computation for a parameter which is live-out.
*) Copy if root does not define buffer no longer necessary because colocated
assignment looks at points-to set of root instruction.

PiperOrigin-RevId: 168412076