Bluetooth: samples: Switch to one-time adv

This patch removes all uses of the adv auto-resume feature in the
Bluetooth samples. The auto-resume feature is planned for deprecation.

Samples that are not intended to demonstrate a technique to do with
re-connection simply do not restart the advertiser, in interest of
simplicity. The user is expected to reboot the sample when needed.

Signed-off-by: Aleksander Wasaznik <aleksander.wasaznik@nordicsemi.no>