arm-safety-island: Enhance HIPC modularity and refine demos recipes

This commit adds a HIPC-specific include file to improve modularity
and updates the zephyr-demos-cl0, zephyr-demos-cl1, and
zephyr-demos-cl2 recipes. Unused configuration options have been
removed for better maintainability.

Signed-off-by: Divin Raj <divin.raj@arm.com>