kernel.core: making some classes final

kernel.core: making some classes final

This patch is to make some classes final in kernel.core component.
It should be final to improve readability and since you should never
extend it. It also allows the jvm to inline methods and improve
performance.

Change-Id: Ie74fb3a6a36075cd355bdc58f4fe1deb3fc4a82a
Signed-off-by: Wassim <wassim.nasrallah.36@gmail.com>
Reviewed-on: https://git.eclipse.org/r/74558
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Hudson CI
Reviewed-by: Genevieve Bastien <gbastien+lttng@versatic.net>
Tested-by: Genevieve Bastien <gbastien+lttng@versatic.net>