Make ForInPrepare take a kRegTriple8 operand and ForInNext take kRegPair8
operand for cache state. This is to ensure that the cache state output of
ForInPrepare is in consecutive registers to allow us to deopt the
ForInPrepare node from TF->Ignition (to be done in a followup CL).

BUG=v8:4280
LOG=N

Review URL: https://codereview.chromium.org/1584813002

Cr-Commit-Position: refs/heads/master@{#33357}