In order to construct the optimal source code combination for functions
(and especially the positions inside the optimal source code for each
function), we need to know all functions upfront.

Rewrite the d8-based snapshotter so that it discovers all objects first
(+ assigns ids), then does the actual snapshotting.

Bug: v8:11525
Change-Id: I4f4e5589575ee9738e8a83aa6cda2c8164803b4c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3268915Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77794}