This makes Liftoff inspection (scope reporting) also use the decoded
names of locals, which are now stored in a C++ data structure (see
https://crrev.com/c/2002541).
The call to {SetOwnPropertyIgnoreAttributes} had to be replaced by a
proper lookup first, to handle integer names and duplicate names
correctly. The test already covered these cases.

The test was extended by another unnamed local to also test the
generation of default names in case no name is provided.

R=thibaudm@chromium.org

Bug: v8:10019
Change-Id: I475bb4db9a32c39203180e9c8d3f8181c3882138
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2002544
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65821}