- Check that internalized strings always have a computed hash value.
- Check that ThinStrings never have a forwarding index.
- Add a simple test of various property access with
  --always-use-string-forwarding-table to make the CF aware of the flag.

Change-Id: Ie047c9f635d5e0ed999208ec3379ef09c395b3f5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3717988Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Patrick Thier <pthier@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81303}