This simplifies NextArrowFunctionInfo, allows us to Scope::Snapshot::Reparent
directly rather than moving it, and allows us to skip reparenting in the simple
parameter arrow function cases.

This is a reland of https://chromium-review.googlesource.com/c/v8/v8/+/1397664,
simply splitting out the arrow-function-name-inferring part.

Change-Id: I640d911a9607edc3bbb0e5ff3bf992094e4159e4
Reviewed-on: https://chromium-review.googlesource.com/c/1397701Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58570}