This reverts commit 026a0c21.

Reason for revert: Reverting due to https://crbug.com/1029461

Original change's description:
> [parser] Fix variable caching for conflict lookup
> 
> During conflict lookup (for lexical variables and sloppy block function
> hoisting), we cache the looked-up variable on the current scope if the
> lookup goes through a ScopeInfo. However, for variable lookup during
> scope analysis, we use the "entry point" as the cache.
> 
> Since both lookups can create Variables, this can cause us to create
> duplicate variables, e.g. a duplicate function name variable in the
> attached test.
> 
> Instead, for ScopeInfo conflict lookups we can cache the result on the
> function's outer scope, which shoud be equivalent to the entry point.
> 
> As a (necessary) drive-by, we can terminate the lookup early if we find
> a VAR with the same name, as we can safely assume that its existence
> means that it doesn't conflict, which means that our variable can't
> conflict either.
> 
> Bug: chromium:1026603
> Change-Id: I19f80f65597ba6573ebe0b48aa5698f55e5c3ea1
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1928861
> Commit-Queue: Leszek Swirski <leszeks@chromium.org>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#65138}

TBR=leszeks@chromium.org,verwaest@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: chromium:1026603
Bug: chromium:1029461
Change-Id: Id7f5dd342e32e1bb57c51b3748feff32ee0ba41d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1958014Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65390}