R1:1f6869a7654a

In "bin/drydock lease", take a JSON "--attributes" so we can accept complex values

Summary:
Depends on D19750. See T13210. The `bin/drydock lease` command makes it easier to request ad-hoc leases, but currently takes lease attributes in the form `--attributes x=y,a=b`.

This was okay for all leases at the time, but doesn't really work for modern WorkingCopy resources since they take a `repositories.map` which has a dictionary as a value. You can't specify that with `repositories.map=...`.

Instead, point…