In contrast to (private) class fields, struct fields are public and
accessed directly, and do not end in an underscore.
This CL fixes naming in struct fields in the recently introduces
{CompilationUnitQueues} class.

R=ahaas@chromium.org

Bug: v8:9183
Change-Id: I87d80650dc4a1c58cf8067ebb4ecfadf929545ab
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1621936Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61687}