During the property lookup, the strings will be internalized anyway.
Doing it early will save the creation of duplicate strings by using the
internalized object right away.
This might fix the GC overhead we see for huge numbers of imports.

R=ahaas@chromium.org

Bug: chromium:1036737
Change-Id: I9c968a0652f394e977c6d061ef157037ebb0f7f9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1993289
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65691}