Add a feedback vector slot for computed property names in object
and class literals. Introduce new slot kind for storing
computed property names.

Change StaDataPropertyInLiteral to use the accumulator (again), so
we don't exceed Bytecodes::kMaxOperands.

We assume that most computed property names are
symbols. Therefore we should see performance
improvements, even if we deal with monomorphic ICs only.

This CL only collects feedback but does not use
it in Reduce() yet.

BUG=v8:5624

Review-Url: https://codereview.chromium.org/2587393006
Cr-Commit-Position: refs/heads/master@{#42082}