MEDIUM: cli: rework the CLI proxy parser

MEDIUM: cli: rework the CLI proxy parser

Rework the CLI proxy parser to look more like the CLI parser, corner
case and escaping are handled the same way.

The parser now splits the commands in words instead of just handling
the prefixes.

It's easier to compare words and arguments of a command this way and to
parse internal command that will be consumed directly by the CLI proxy.