[Proposal] Ensure `leo add` always stores dependencies locally

[vicsn]

💥 Proposal

Currently, leo add may either:

• point to a local dependency
• point to a virtual yet-to-be-downloaded runtime network dependency

However, the difference in behaviour as well as the resulting program.json entry is confusing:

      "location": "network",
      "path": null

I would propose for --network to require a <URL> parameter, and to immediately download the dependency, e.g. from a local devnet or from canary/testnet/mainnet.

The only reason I can imagine for requiring a dynamic network fetch, is when the user is testing and deploying multiple novel programs. In which case, they will by necessity have defined them locally anyway.

To maintain backwards compatible, we could adjust the CLI behaviour, but still support location: network in program.json for a while or potentially forever.

[vicsn]

Updates:

• it seems actually useful to be able to specify --network so you don't have to redeploy (and pay for the time and the fee!)
• however, what about deployments of multiple local dependencies failing halfway? We should have a solid way of preventing redeployment, the --skip flag is not safe by default.