Fix crash in JSPromise::Resolve when 'then' getter is terminating

The crash scenario is as follows:
  1) Add a getter for 'then' to the Object prototype that is
     considered side-effecting.
  2) Evaluate a simple string using 'REPL' mode with side-effect checks
     enabled.
     Note: REPL mode is not strictly necessary, but it causes a 'then'
     lookup as the evaluation result is not a promise.
  3) Calling the 'then' getter causes a termination exception, due
     to the side-effect check. JSPromise::Resolve then tries to
     put the termination exception as the reject reason, which causes
     a CHECK failure.

The solution is to check for termination in the "abrupt completion"
case when 'then' was retrieved.

Bug: chromium:1140845
Change-Id: I72b644cd49355cea40f599fcbe80264e99ed7bd6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2501283


Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70785}