In order to improve our tiering strategy, it is a good idea to start
by tiering up functions that will be used the most, as this is done in
most JavaScript engines.

To decide which function requires tiering, we use as a basic strategy
to define its compilation priority to 'func_size * number_of_calls',
this roughly approximates the time we spend in the function.

To handle prioritization, it seemed that using  a concurrent
priority queue similar to BigUnits was causing concurrencies issues.
I then decided to use different priority queues for each worker thread.

R=clemensb@chromium.org
CC=thibaudm@chromium.org

Bug: v8:10728
Change-Id: I6f314468549000b2a9b51d3d470f04a0cb997879
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2367859
Commit-Queue: Arnaud Robin <arobin@google.com>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69585}