When deciding whether we need to create a full-blown `arguments` object,
we look at various things, starting as early as in the parser.
Until now, if the parser saw the identifier `arguments`, we'd decide
that it's enough of a clue that we should create the `arguments` object
since somebody is obviously accessing it.
However, that missed the case where someone is just accessing a property
named `arguments` on some object. In such cases (`o.arguments`), we now
hold off on creating an `arguments` object.
~11% speed-up on Octane/typescript.js :^)
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