Now that instruction cache flushing is process-wide and no longer bound
to a specific {Isolate}, we can also make setters on the {RelocInfo}
structure equally independent of the {Isolate} and remove the respective
parameter everywhere.

R=ahaas@chromium.org

Change-Id: I7b21f6f79d0d6cf73424019b9e808c3ec76de08e
Reviewed-on: https://chromium-review.googlesource.com/915922Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51269}