Implement --no-exec option for import-url command #3513
Description
dvc import-url creates new .dvc file, just as dvc run. Sometimes files which would be imported are already present locally and it's quite inconvenient that they should be downloaded again in order to create a pipeline step.
Because of that it would be great to add --no-exec option: we create pipeline step, then use dvc commit to update its md5 with already downloaded file.