With concurrent inlining, the inlining phase happens on the background
thread and the data needed for the inlining phase is serialized on
the main thread. The serialization phase tries to gather data about
functions called which is sometimes more expensive than inlining phase
itself. So it's better not to use concurrent inlining for TurboFan
compilations when tiering up from Turboprop to TurboFan. Turboprop
compilations don't inline and hence it is OK to continue using
concurrent inlining for Turboprop compilations.

Bug: v8:9684
Change-Id: Ib529905213fa7f0df84ee52218adc27f7c219f60
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2557504
Commit-Queue: Mythri Alle <mythria@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71405}