Reland Vector ICs: platform support for vector-based stores.

Reland Vector ICs: platform support for vector-based stores.

The last changes for vector store functionality, they are in 3 areas:

1) The new vector [keyed] store code stubs - implementation.
2) IC and handler compiler adjustments
3) Odds and ends. A change in ast.cc, a test update, a small Oracle fix.

TBR=bmeurer@chromium.org, jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1319123004

Cr-Commit-Position: refs/heads/master@{#30581}