ivi-shell: add new signal to notify ivi shell destroying

In the case the controlelrs are depended on ivi-shell resource,
it must be destroy before the ivi shell destroy. To do this,
add new ivi shell destroy signal on ivi shell, emit it on
the begining of the shell destroying

Suggested-by: Harsha M M <harsha.manjulamallikarjun@in.bosch.com>
Suggested-by: Michael Olbrich <m.olbrich@pengutronix.de>
Suggested-by: Marius Vlad <marius.vlad@collabora.com>

Signed-off-by: Tran Ba Khang(MS/EMC31-XC) <Khang.TranBa@vn.bosch.com>