WIP: rust: lock: Add B::is_locked() assertion to Guard::new()

TODO: turn this into its own commit in preparation for making Guard::new()
public

rust/kernel/sync/lock.rs

@@ -252,6 +252,9 @@ impl<'a, T: ?Sized, B: Backend> Guard<'a, T, B> {
         state: B::GuardState,
         _context: B::Context<'a>,
     ) -> Self {
+        // SAFETY: The lock is guaranteed to be initialized by `Lock`'s type invariants
+        debug_assert!(unsafe { B::is_locked(lock.state.get()) });
+
         Self {
             lock,
             state,