The feature comes from the "x-deprecated" field in schemas (any schema that is used
to parse arguments), and can be a boolean or a string.
The parser now takes a logger and will warn users when encountering a deprecated
option. These options will also appear in JSON help.
SubCommands are not tied to the option that triggers them. They
contain a subset of a CommandDescription interface, with at least
a short and long description and usage notes. These are generated
from the subcommand schema (e.g. schematics in case of generate).
