This reverts commit d8f564ea.

Reason for revert: Breaks mac asan (https://build.chromium.org/p/client.v8/builders/V8%20Mac64%20ASAN/builds/17067)

Original change's description:
> Reland: Remove SFI code field
> 
> Remove the SharedFunctionInfo code field, inferring the code object
> from the function_data field instead. In some cases, the function_data
> field can now hold a Code object (e.g. some WASM cases).
> 
> (Reland of https://chromium-review.googlesource.com/952452)
> 
> TBR=mstarzinger@chromium.org
> 
> Bug: chromium:783853
> Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
> Change-Id: I10ea5be7ceed1b51362a2fad9be7397624d69343
> Reviewed-on: https://chromium-review.googlesource.com/970649
> Commit-Queue: Leszek Swirski <leszeks@chromium.org>
> Reviewed-by: Yang Guo <yangguo@chromium.org>
> Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Leszek Swirski <leszeks@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#52136}

TBR=yangguo@chromium.org,mstarzinger@chromium.org,jgruber@chromium.org,leszeks@chromium.org

Change-Id: I348ec7a9d837a7b068fd08312b77e87abf21be7b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:783853
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/975305Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52143}