Kernel: Make Inode::register_watcher() OOM-fallible

Author: https://github.com/IdanHo
Commit: a9cd8ca841
Pull-request: https://github.com/SerenityOS/serenity/pull/12128
Reviewed-by: https://github.com/bgianfo ✅

Kernel/FileSystem/Inode.h

@@ -91,7 +91,7 @@ public:
 
     bool has_watchers() const { return !m_watchers.is_empty(); }
 
-    void register_watcher(Badge<InodeWatcher>, InodeWatcher&);
+    ErrorOr<void> register_watcher(Badge<InodeWatcher>, InodeWatcher&);
     void unregister_watcher(Badge<InodeWatcher>, InodeWatcher&);
 
     ErrorOr<NonnullRefPtr<FIFO>> fifo();