tests: arch: arm: increase main stack size for no-opt interrupt test

Tests fail with the default 512 byte main stack size.  Increase it
just as the idle stack size has been increased over default.

Closes #20202

Signed-off-by: Peter Bigot <[email protected]>

Author: pabigot

tests/arch/arm/arm_interrupt/testcase.yaml

@@ -10,3 +10,4 @@ tests:
     extra_configs:
       - CONFIG_NO_OPTIMIZATIONS=y
       - CONFIG_IDLE_STACK_SIZE=512
+      - CONFIG_MAIN_STACK_SIZE=1024