Also add more test cases of Array lastIndexOf with proxy, inspired by test262.

In the path for sparse arrays, no changes are needed because element accesses
are not observable there (thanks to UseSparseVariant).

Bug: v8:7813
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: Ifd47149f654e92f56d0a1ed6b3debc93718702be
Reviewed-on: https://chromium-review.googlesource.com/1160307
Commit-Queue: Hai Dang <dhai@google.com>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54887}