kconfig: default to LEGACY_INCLUDE_PATH=n

Change the default config for LEGACY_INCLUDE_PATH to 'n'.

This makes any test or sample fail CI if there's any #include missing
the "zephyr/" prefix.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>

Author: fabiobaltieri

Kconfig.zephyr

@@ -845,7 +845,6 @@ endmenu
 
 config LEGACY_INCLUDE_PATH
 	bool "Allow for the legacy include paths (without the zephyr/ prefix)"
-	default y
 	help
 	  Allow applications and libraries to use the Zephyr legacy include
 	  path which does not use the zephyr/ prefix. For example, the