Turbofan support for property loads from module namespace objects
has been tested by the test/js-perf-tests/Modules/basic-namespace
benchmark, but so far not by the mjsunit suite. This CL adds such
a test.
This is a follow-up to 8d7379c0.

Change-Id: I3c4183d761693199e6bc8740b812279efcd791a0
Reviewed-on: https://chromium-review.googlesource.com/1142594Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54535}