Enabling concurrent inlining builds the graph on background thread
reducing the time spent on main thread.

Bug: v8:9684
Change-Id: Iee00aa991ab8e14fad76b0d9c0b0fd9f8d1eecde
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1937149Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65202}