This is a partial reland of https://crrev.com/c/3597106 , except for the
changes in compiler.cc, which are just the minimal possible changes to
make the code compile.

With this change, it is possible that a call to
CompilationCache::LookupScript returns any of:
1. A Script and a toplevel SharedFunctionInfo (cache hit)
2. A Script but no toplevel SharedFunctionInfo (partial cache hit)
3. Nothing (cache miss)

Bug: v8:12808
Change-Id: Id33a4cd0cb28562d6b862fbb113ea9d03f255b2b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3687425Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#81193}