twister: verify all platform names
twister: verify all platform names

Fix bug in verify_platforms_existence method - make it possible to
verify all platform names from list - not only first.

Fixes: #48321

Signed-off-by: Piotr Golyzniak <77503f07a08667f008ecbe02e9a32eb51adc160d@nordicsemi.no>

galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr