{WasmInstanceObject} is a {JSObject}, so it can have user-defined
properties and elements. DebugPrint should include them.

R=titzer@chromium.org

Change-Id: Id787fc2d40c256a0287aea69353066c6fd920a56
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1541236Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60491}