bsim: Bluetooth: Mesh: Add suspension test

Adds two test-cases; one for suspending and resuming Mesh,
and one for suspending Mesh and disabling Bluetooth before
re-enabling Bluetooth and resuming Mesh.

Both tests checks that periodic publication is stopped during
suspension.

Signed-off-by: Håvard Reierstad <haavard.reierstad@nordicsemi.no>