rust: debugfs: support binary large objects for ScopedDir

rust: debugfs: support binary large objects for ScopedDir

Add support for creating binary debugfs files via ScopedDir. This
mirrors the existing functionality for Dir, but without producing an
owning handle -- files are automatically removed when the associated
Scope is dropped.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Matthew Maurer <mmaurer@google.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>