This is a first step towards allowing expressions for array sizes.

So far, local variable bindings used a VisitResult and a const flag.
This doesn't allow for local bindings to alias other things, like
heap references. While this is not generally a feature we need,
it will be helpful to create bindings when evaluating array sizes,
since we want to grant access to the preceding already initialized
object fields, but not to the whole object, which is not completely
initialized yet.

LocationReference already captures the notion of any readable and
assignable location, so it is a good fit to be used for local bindings.
The const attribute is no longer needed, since LocationReference already
has a notion of constness for stack ranges (that is,
LocationReference::Temporary vs LocationReference::VariableAccess).

Bug: v8:10004 v8:7793
Change-Id: Ibe0a43e898e5c2c10d6739e2496d92dda542e6cc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1928852Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65117}