feat: parse connection string as address with user

Refactor address parsing in CLI:

• picodata connect [user@][host][:port]
• picodata run --peer
• picodata run --listen
• picodata run --http-listen
• picodata run --advertise
• picodata expel --peer

Only picodata connect respects the username. Other options just ignore it.

• Provide new struct Address
• Replace try_parse_address function with impl FromStr for Address.
• Provide both unit and pytests

Close #252 (closed).