Revert of [stubs] KeyedLoadIC_Generic: prototype chain lookup support (patchset #2 id:20001 of https://codereview.chromium.org/2652213003/ )

Reason for revert:
Speculative revert for breaking a layout test:
https://build.chromium.org/p/client.v8.fyi/builders/V8-Blink%20Linux%2064/builds/13113

Unfortunately, the test results archive is not giving much info this time.

Original issue's description:
> [stubs] KeyedLoadIC_Generic: prototype chain lookup support
>
> Performing lookups on the prototype chain in the stub avoids a
> bunch of slow-path runtime calls. For now, only receivers with
> dictionary-mode properties do this; fast-mode receivers will follow
> if it's beneficial.
>
> Review-Url: https://codereview.chromium.org/2652213003
> Cr-Commit-Position: refs/heads/master@{#42751}
> Committed: https://chromium.googlesource.com/v8/v8/+/82e10f5fbacbbd71bc65e99322f432470692bf41

TBR=ishell@chromium.org,jkummerow@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review-Url: https://codereview.chromium.org/2657393002
Cr-Commit-Position: refs/heads/master@{#42754}