FeedbackSlotIterator abstracts over the different IC states and
provides an unified interface to iterate over the map and handlers in
the IC.

Bug: v8:10582
Change-Id: I67861bfbd33d82e8b1ad06156fbf6fd72775321c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2349295
Commit-Queue: Sathya Gunasekaran  <gsathya@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69357}