Replaces the use of KeyedStoreICGeneric with a vector based KeyedStoreIC for
array literal computed stores now that there is a feedback vector slot for
these expressions. Removes KeyedStoreICGeneric bytecode since this is no
longer necessary.

BUG=v8:4280
LOG=N
TBR=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/1400353002

Cr-Commit-Position: refs/heads/master@{#31262}