[OSCBS-41] Update to Zephyr v3.2.0 (#382)

Updating to integrate with Zephyr v3.2.0 required:

- Update `west.yml` to import Zephyr v3.2.0 manifest
- Prefix include pathname of ztest.h with `zephyr/`
- Prefix every Zephyr header included pathname with `zephyr/`
- Change all Zephyr tests/samples to use `find_package`
- For unit_testing, use a distinct prj.conf which only references
  Kconfigs defined in the Zephyr repo. (Zephyr constraint.)
- Move ztest headers into a zephyr-prefixed pathname

Co-authored-by: Gregory Shue <gregory.shue@legrand.com>

ports/zephyr/datetime-init.c

@@ -14,6 +14,8 @@
 #include <stdlib.h>
 #if CONFIG_NATIVE_APPLICATION
 #include <sys/time.h>
+#elif defined(__ZEPHYR__)
+#include <zephyr/posix/sys/time.h>
 #else
 #include <posix/sys/time.h>
 #endif