app: zephyr: enable CONFIG_ASSERT in debug overlay

Enable CONFIG_ASSERT=y in SOF debug overlay.

Also add a commented out list of additional useful Zephyr debugging
tools to the overlay. These incur a higher runtime cost, so are left
disabled by default. These are all debug tools that have been tested to
work with SOF and found useful.

Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>

app/debug_overlay.conf

@@ -1 +1,11 @@
 CONFIG_DEBUG=y
+CONFIG_ASSERT=y
+
+# Following options can be enabled additionally,
+# but will incur a higher runtime cost, so are thus
+# disabled by default.
+#
+# CONFIG_STACK_SENTINEL=y
+# CONFIG_SYS_HEAP_VALIDATE=y
+# CONFIG_SPIN_VALIDATE=y
+# CONFIG_SPIN_LOCK_TIME_LIMIT=50000