This CL simplifies IC code since we no longer need to keep
feedback slot indices in both Smi and IntPtr form and as
a result it should improve overall performance of --no-opt
mode on Octane by ~1%.

Bug: v8:10047
Change-Id: Ib717697cdb805c9f93286e9c62ee8a63361d3560
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1965586
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66585}