Update to reflect FlowSensitive API changes: `RecordValue` removed

`RecordValue` was used as a wrapper to bring a prvalue and its `RecordStorageLocation` together:
we were using it to track iterators by keeping their `Value`.
To overcome this change, we should instead keep their `RecordStorageLocation`.

Moreover, now records can't be directly associated with values:
so it isn't possible to get a container value from its expression (because it is a record).
To overcome this change, a new synthetic field, that stores the container which the iterator refers to, has been added.

Change-Id: Ie8d1b9123027cd0f031d15d9072d0f4f97c06e60
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5526441


Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Reviewed-by: Paul Semel <paulsemel@chromium.org>
Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1304292}