This API was used for IndexedDB support and for transferring modules by
serializing and deserializing (before we were sharing code between
isolates). Last uses were removed in https://crrev.com/c/1847366, thus
this whole API is unused by now.
This CL deprecates the API and refactors tests to use the internal APIs
instead.

R=adamk@chromium.org

Bug: v8:10146
Change-Id: I838039b4be7ea4eebe6769f31f48e51e7bcd4645
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2006090
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65908}