In the --turbo-nci-as-highest-tier testing mode, allow NCI codegen for
OSR to increase coverage and simplify logic.

Bug: v8:8888
Change-Id: I254939928f92bf675dbf2b78cdd5b5dce802d972
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2339460
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69262}