Fix the `_load_model` method of `CLIProject`. Before this commit it
erroneously did not call `_set_model` on all codepaths, resulting in
cases where `self.model` was incorrectly missing the `_project` field.
When producing artifacts, if the rank is 0 the only element should be
extracted from the produced dict. Fix a wrong assertion that checked
that the returned dict has 0 keys instead of 1.
Add a python interface (`revng.profile`) for interacting with the rev.ng
infrastructure as a whole; either through the CLI (`CLIProject`) or the
GraphQL API (`DaemonProject`).
Giacomo Vercesi