This pretty much rewrites the preparsed scope data collection. We used to store
the allocation result, but it's faster to just store the raw data which is
needed for deciding it later. (This way we don't need to run the allocation
algorithm for just getting this data.)

For each variable: is_used, maybe_assigned,
has_forced_context_allocation, and for each scope:
inner_scope_calls_eval_.

In addition, this CL moves data handling out of Scope and into
PreParsedScopeData where it belongs and simplifies the API for
PreParsedScopeData.

BUG=v8:5516
R=vogelheim@chromium.org

Change-Id: Ia5a4fa52f585cd4f483ce9a92f2dd7d9754f34ed
Reviewed-on: https://chromium-review.googlesource.com/451273
Commit-Queue: Marja Hölttä <marja@chromium.org>
Reviewed-by: Daniel Vogelheim <vogelheim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43641}