refactor: cli address parsing

The following commands are affected:

- `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