Drive-by fixes:
 - Use constexpr types to determine C++ type names.
 - Fix factory constructors to not skip write barriers in old generation.

Change-Id: I0ebbfd56c06ad41d02836fb48531ae7eded166bf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2400994Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70921}