twister: raise error for non-existing platform call

Changes will raise error and break program in following three situations:

1. Platform name pass in --platform option does not exist.
2. During using --all option, platform from platform_allow list does not
exist.
3. During using --integration option, platform from
integration_platforms list does not exist.

Signed-off-by: Piotr Golyzniak <piotr.golyzniak@nordicsemi.no>