LibCore: Implement File::can_delete_or_move()

Besides from a general check if a file's directory has write
permissions, this also checks if the directory has set a sticky bit,
meaning that only file owners and the directory owner can remove or move
files in such directory. It's being used in /tmp for example.

Userland/Libraries/LibCore/File.h

@@ -53,6 +53,7 @@ public:
     static ErrorOr<size_t> size(DeprecatedString const& filename);
     static DeprecatedString current_working_directory();
     static DeprecatedString absolute_path(DeprecatedString const& path);
+    static bool can_delete_or_move(StringView path);
 
     enum class RecursionMode {
         Allowed,