Remove the explicit script handle from ParseInfo, and make it either
a Handle that is passed around where needed, or one inferred from the
SharedFunctionInfo.

This will be useful for compilation finalization using the off-thread
factory, which will not generate real Handles since it has no access
to the Isolate.

Bug: chromium:1011762
Change-Id: I5d9564009ec83bb9fc74191b4aa69735d132c2f7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1977861Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65629}