[XLA] Modify the function that determines whether an instruction can change

layout so that it can be used by the HLO verifier.

Change the function to a static member function of the LayoutAssignment class.

Add an std::function member to LayoutAssignment to store the function object
passed down from the backend compiler class and use it to decide whether an
instruction can change layouts.

Fix affected test cases.

PiperOrigin-RevId: 215515611