ActiveStorage subscriber can leak potential sensitive/pii fields


For instance, the `key` here
https://github.com/rails/rails/blob/a8709e6ea26eca73a652af4fdd0a9f7db5352af4/guides/source/active_support_instrumentation.md?plain=1#L870

Guard these behind `send_default_pii`

