Turbopack: Simplify parent directory creation retry loop logic (#95835)
Noticed while reading through the symlink code.
The symlink logic had some clever `ErrorKind::AlreadyExists` logic that
folded the retry into the main retry loop, but we still had a separate
retry loop for after handling `ErrorKind::NotFound`. This folds the
loops together.
I hand-implemented the symlink version of this and had opus port it to
the non-symlink version.