Revert of [wasm] Refactor function name table and lookup (patchset #2 id:20001 of https://codereview.chromium.org/2057523002/ )

Reason for revert:
[Sheriff] Speculative revert for flaky gc stress crashes, e.g.:
https://build.chromium.org/p/client.v8/builders/V8%20Mac%20GC%20Stress/builds/6592
https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20GC%20Stress%20-%20custom%20snapshot/builds/6143

Original issue's description:
> [wasm] Refactor function name table and lookup
>
> The function name table will now always be set; a CHECK will fail if
> the length would exceed the integer range.
> Also, the resolution of undefined function names to "<WASM UNNAMED>" is
> moved over to the wasm side.
>
> R=titzer@chromium.org
>
> Committed: https://crrev.com/3400ee9f4f21a455b7850ec42a4182a3c0eba310
> Cr-Commit-Position: refs/heads/master@{#36918}

TBR=titzer@chromium.org,clemensh@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/2062793002
Cr-Commit-Position: refs/heads/master@{#36925}