search.processing.JobManager

Use LinkedList instead of manually maintained array based queue.

Change-Id: I88e72428a6730333807ca04c3cd115241af676d9
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>
Reviewed-on: https://git.eclipse.org/r/c/jdt/eclipse.jdt.core/+/183141
Tested-by: JDT Bot <jdt-bot@eclipse.org>