`Device::destroy` should take effect immediately

There is a comment in `device_destroy` describing, and code in in `Device::maintain` implementing device destruction (which involves calling the device loss callback) only after the queue is drained. This was correct under an earlier version of the spec, but as of https://github.com/gpuweb/gpuweb/pull/4903, is no longer correct. Device destruction should take effect immediately. Related: #9278, which is about needing to poll the device in order for the device lost callback to be invoked.