ss: Change datastore.tests to a fragment plug-in

ss: Change datastore.tests to a fragment plug-in

This will allow us to use the same package names in the test
classes as the runtime ones. That way tests will have access
to package-visible (default visibility methods).

This will remove the need of having tons of public methods just
for testing. Default-visibility methods (or even protected, where
needed) are arguably much safer, and won't risk confusing future
clients.

Change-Id: I0393ac9103f94afcb9a818cbe2e7c8dfcadcac18
Signed-off-by: Alexandre Montplaisir <alexmonthy@efficios.com>
Reviewed-on: https://git.eclipse.org/r/87163
Reviewed-by: Hudson CI
Reviewed-by: Genevieve Bastien <gbastien+lttng@versatic.net>
Tested-by: Genevieve Bastien <gbastien+lttng@versatic.net>