Reland of [wasm] Enforce that function bodies end with the \"end\" opcode. (patchset #1 id:1 of https://codereview.chromium.org/2628883006/ )

Reason for revert:
Try a reland; this might not have been the source of tree-closing.

Original issue's description:
> Revert of [wasm] Enforce that function bodies end with the \"end\" opcode. (patchset #3 id:40001 of https://codereview.chromium.org/2630553002/ )
>
> Reason for revert:
> Caused tree to close by failing compilation:
>
> https://build.chromium.org/p/client.v8/builders/V8%20Win64%20-%20clang/builds/4451
>
> Original issue's description:
> > [wasm] Enforce that function bodies end with the \"end\" opcode.
> >
> > R=rossberg@chromium.org
> > BUG=chromium:575167
> >
> > Review-Url: https://codereview.chromium.org/2630553002
> > Cr-Commit-Position: refs/heads/master@{#42286}
> > Committed: https://chromium.googlesource.com/v8/v8/+/fcc6e85ec6b01e5367795f98aff104b1ff23f619
>
> TBR=mtrofin@chromium.org,rossberg@chromium.org,jbroman@chromium.org,titzer@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=chromium:575167
>
> Review-Url: https://codereview.chromium.org/2628883006
> Cr-Commit-Position: refs/heads/master@{#42287}
> Committed: https://chromium.googlesource.com/v8/v8/+/1d32a3989bc474745eeb618ebf094634f4efbb36

TBR=mtrofin@chromium.org,rossberg@chromium.org,jbroman@chromium.org,titzer@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:575167

Review-Url: https://codereview.chromium.org/2628203003
Cr-Commit-Position: refs/heads/master@{#42296}