[nrf fromlist] tests: secure_storage: its: increase stack sizes

Some implementations require more stack than others.
Increase the Ztest and main stack sizes to accommodate them.

Signed-off-by: Tomi Fontanilles <[email protected]>

Upstream PR #: 85735

(cherry picked from commit abc9cb2710efaf5548d95c8bdc0da274fb90892a)
Signed-off-by: Tomi Fontanilles <[email protected]>

Author: tomi-font

tests/subsys/secure_storage/psa/its/overlay-secure_storage.conf

@@ -1,4 +1,4 @@
-CONFIG_ZTEST_STACK_SIZE=3072
-CONFIG_MAIN_STACK_SIZE=2048
+CONFIG_ZTEST_STACK_SIZE=4096
+CONFIG_MAIN_STACK_SIZE=3072
 
 CONFIG_SECURE_STORAGE=y