[turbofan] add MachineType to AllocatedOperand

[turbofan] add MachineType to AllocatedOperand

- allows the optimization of emitted gap move code since the representation of the value in the register is known
- necessary preparation for vector register allocation
- prepare for slot sharing for any value of the same byte width

BUG=

Review URL: https://codereview.chromium.org/1087793002

Cr-Commit-Position: refs/heads/master@{#28137}