This removes the last use of %AppendElement (and the function itself),
which was in the pattern rewriter's code for destructuring assignment
with an array rest pattern. In its place, it introduces a
StoreInArrayLiteral AST node that corresponds to the StoreInArrayLiteral
bytecode (which in turn corresponds to the StoreInArrayLiteral IC).

Change-Id: I1d212407b025cf0919263d119f6f47c88bd9a71e
Reviewed-on: https://chromium-review.googlesource.com/955307
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51898}